localize-cy

Localize: Welsh (cy → Cymraeg) — High-Fidelity Skill

Scope & Variants

Welsh (Cymraeg) is the Celtic language of Wales. The default and primary target for product localization is Welsh Standard Written — the unified literary/professional written register used across Wales for government, education, broadcasting, and software UI.

Locale	Notes
cy / cy-GB	Welsh (Wales). Default and primary target. Welsh Standard Written form covers all UI work.
Northern Welsh (Gogledd)	Colloquial spoken variant — does NOT diverge in written/UI contexts.
Southern Welsh (De)	Colloquial spoken variant — does NOT diverge in written/UI contexts.

Practical reality: Welsh has a strong written standard (sometimes called Cymraeg safonol or Cymraeg llenyddol) that is used uniformly across Wales for UI, government, broadcasting, and education. Northern and Southern Welsh diverge in spoken pronunciation, lexicon (e.g., llefrith North vs llaeth South for "milk"), and some verb forms (e.g., dwi'n North vs rwy'n South for "I am"), but these regional differences are largely absent from the written standard used in software localization.

The defining quality concern in Welsh localization is correct application of initial consonant mutations. Mutations are not optional or stylistic — they are mandatory orthographic changes triggered by specific grammatical environments. A Welsh translation with missing or wrong mutations reads as fundamentally broken to a native speaker, even if the rest of the text is correct.

Welsh is a Celtic Brittonic language

Welsh is one of the four surviving Celtic languages, in the Brittonic (Brythonic, P-Celtic) branch:

Branch	Languages
Brittonic (P-Celtic) — Welsh's family	Welsh (Cymraeg), Cornish (Kernewek), Breton (Brezhoneg)
Goidelic (Q-Celtic) — DIFFERENT family	Irish (Gaeilge), Scottish Gaelic (Gàidhlig), Manx (Gaelg)

Welsh shares structural features with Cornish and Breton (mutations, VSO word order, inflected prepositions) but is NOT mutually intelligible with Irish or Scottish Gaelic, despite popular conflation. Calling Welsh "Gaelic" is wrong.

Welsh is also NOT English. Despite Wales sharing the island of Great Britain with England and the deep historical contact between the two languages, Welsh is structurally unrelated to English. Welsh has VSO word order (not SVO), initial consonant mutations (not present in English), inflected prepositions (English has none), and no indefinite article (English has "a/an"). Treating Welsh as "English in disguise" is the most common source of bad Welsh translations.

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Identity Guardrail — Welsh is NOT Gaelic and NOT English

Auto-fail signals (translator is treating Welsh as the wrong language):

Signal	Diagnosis	Fix
Output uses Sláinte, Slán, Fáilte	Translator wrote Irish, not Welsh	"Welcome" = Croeso; "Goodbye" = Hwyl fawr
Output uses Gaelic accent marks like à è ì ò ù	Irish/Scottish Gaelic uses grave accents	Welsh uses circumflex (to bach): â ê î ô û ŵ ŷ — never grave
Output is SVO (subject-verb-object) word order	Translator used English structure	Welsh is VSO — verb first: Cadwodd y defnyddiwr y ffeil
Output mutations missing or incorrect	Translator skipped Welsh-specific grammar	Apply soft/nasal/aspirate mutation per trigger
Output uses the before nouns mechanically	English calque	Welsh has only definite article (y/yr/'r) and NO indefinite article
Output uses of construction (car o John)	English calque	Welsh uses juxtaposition for possession: car John
Output reads like word-for-word English	English SVO retained	Restructure as VSO with periphrastic bod + yn + verbal noun

Cultural note: Welsh has Equal Status with English in Wales under the Welsh Language (Wales) Measure 2011. The Welsh Government's strategy Cymraeg 2050 aims for one million Welsh speakers by 2050. The Cymraeg Clir (Plain Welsh) movement promotes accessible, clear Welsh in public communications. Welsh-language-medium contexts (Welsh-medium schools, Welsh-language broadcasting, government bilingual services) are politically and culturally significant. Sloppy or anglicism-heavy Welsh is not just bad style — it is read as disrespect for the language.

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Register Auto-Detection (Apply Before Translating)

Welsh has a T-V distinction:

Pronoun	Use	Possessive	Verb ending (imperative)
chi	Formal singular OR plural (any number)	eich (no mutation)	-wch (Cadwch, Dewiswch)
ti	Informal singular only	dy (+ soft mutation)	-a / -â (Cadwa, Dewisa)

Auto-detect from source:

Source signal	Target register
Professional product UI / business / government (DEFAULT)	chi formal — eich, -wch imperatives, native Welsh vocabulary
Casual app / social / children's software	ti informal — dy + soft mutation, -a imperatives
Marketing copy (warm but professional)	chi formal — Welsh marketing is typically formal/respectful
Legal / banking / official	chi formal — never ti for institutional voice

Hard rule: never mix chi and ti in the same text.

• ✗ Cadwch eich gwaith + Dewisa — mixes chi imperative with ti imperative
• ✗ Gallwch chi newid dy osodiadau — chi verb form with ti possessive

Special UI exception — verbal-noun buttons are register-neutral: Welsh UI buttons use the berfenw (verbal noun) form, which is neither chi nor ti — it's the bare verb form: Cadw, Dileu, Copio, Agor. This is the established Microsoft/Apple/LibreOffice/Welsh Government convention. Button labels do NOT change between chi and ti registers.

Surface	chi form	ti form	Verbal-noun (buttons)
Imperative ("Save!")	Cadwch	Cadwa	—
Button label	—	—	Cadw
Possessive ("your file")	eich ffeil	dy ffeil	—
Instruction in body text	Dewiswch eich ffeil	Dewisa dy ffeil	—

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Critical Hard Rules (Severity ≥ 2.0 — Auto-Fail If Wrong)

1. Initial Consonant Mutations — THE defining Welsh feature (severity 2.5)

Welsh mutations change the first letter of a word based on the grammatical environment. There are three mutation systems: soft (treiglad meddal), nasal (treiglad trwynol), and aspirate (treiglad llaes). Mutations are not optional; they are part of the word's spelling in that context.

1a. Soft Mutation (Treiglad Meddal) — most common

The soft mutation softens stops to voiced/fricative equivalents:

Original	Soft mutation	Example trigger	Example
c	g	dy (your-ti)	dy gar (your car) ← car
p	b	i (to)	i Baris ← Paris
t	d	o (from)	o Ddenmarc ← Tdenmarc... actually: o Denmarc ← Denmarc
g	(dropped — ∅)	dy (your-ti)	dy ardd ← gardd (your garden)
b	f	dy (your-ti)	dy frawd ← brawd (your brother)
d	dd	dy (your-ti)	dy ddrws ← drws (your door)
m	f	y (fem. art.)	y ferch ← merch (the girl)
ll	l	dy (your-ti)	dy law ← llaw (your hand)
rh	r	dy (your-ti)	dy riant ← rhiant (your parent)

Soft mutation triggers (the most important set to memorize):

Trigger	Meaning	Example
dy	your (ti, informal)	dy gar (your car)
ei	his	ei dad (his father)
y / yr / 'r	the (only before feminine singular nouns)	y ferch (the girl)
i	to	i Gaerdydd (to Cardiff)
o	from / of	o Lundain (from London)
am	about, at (time)	am dri (at three)
ar	on	ar gadair (on a chair)
at	towards	at Ddi (to you-ti)
gan	by, with	gan ferch (by a girl)
heb	without	heb garden (without a garden... actually gardd)
tan / dan	under, until	dan fwrdd (under a table)
dros	over, for	dros bonthwy (over a bridge... pont)
drwy / trwy	through	drwy goeden (through a tree)
wrth	by, while	wrth gadw (while saving)
hyd	until	hyd fory (until tomorrow)
neu	or (sometimes)	A neu B (or; usually no mutation in modern Welsh)
yn (predicative, before adj./noun)	"is" + complement	Mae'n ddiddorol ← diddorol (it is interesting)
yn (adverbial, before adj.)	-ly	yn gyflym ← cyflym (quickly)
dau / dwy	two (m./f.)	dau gi (two dogs); dwy ferch (two girls)
tri / tair	three (m./f.)	(note: tri takes aspirate, not soft — see below)
prif	main, chief (precedes noun)	y prif beth (the main thing) ← peth
hen	old (precedes noun)	hen dŷ (an old house) ← tŷ
Feminine singular noun → adjective after it		merch ddal ← tal (a tall girl)
Object of inflected (conjugated) verb	direct object soft-mutates	Gwelais gi ← ci (I saw a dog)

1b. Nasal Mutation (Treiglad Trwynol)

The nasal mutation converts stops to their nasal equivalents:

Original	Nasal mutation	Example trigger	Example
c	ngh	fy (my)	fy nghar ← car (my car)
p	mh	fy (my)	fy mhen ← pen (my head)
t	nh	fy (my)	fy nhad ← tad (my father)
g	ng	fy (my)	fy ngardd ← gardd (my garden)
b	m	fy (my)	fy mrawd ← brawd (my brother)
d	n	fy (my)	fy nrws ← drws (my door)

Nasal mutation triggers (only two real triggers):

Trigger	Meaning	Example
fy	my	fy nghar (my car)
yn (as locative preposition "in")	in [place]	yng Nghaerdydd ← Caerdydd (in Cardiff). Note: yn itself becomes ym before m-/mh-, yng before ng-/ngh-.

Critical: yn has three different functions and mutations. See §1d below.

1c. Aspirate Mutation (Treiglad Llaes)

The aspirate mutation affects ONLY c, p, t, converting them to fricatives:

Original	Aspirate mutation	Example trigger	Example
c	ch	ei (her)	ei char ← car (her car)
p	ph	a (and)	a phleser ← pleser (and pleasure)
t	th	ei (her)	ei thad ← tad (her father)

Aspirate mutation triggers:

Trigger	Meaning	Example
ei	her	ei thad (her father)
a	and	bara chaws ← caws (bread and cheese)
â	with (instrument)	â chyllell ← cyllell (with a knife)
gyda	with	gyda phleser (with pleasure)
tri	three (m.)	tri chi ← ci (three dogs)
chwe	six	chwe phunt ← punt (six pounds)
tua	about, approximately	tua thri (about three)

1d. The Three Faces of yn — Critical Disambiguation

Welsh yn has three completely different uses, each triggering a different mutation (or none):

Function	Mutation	Example
Progressive aspect (before verbal noun) — "is doing"	NO mutation	Mae'n cadw (he/she is saving). NOT Mae'n gadw.
Adverbial (before adjective, makes -ly)	Soft mutation	yn gyflym (quickly) ← cyflym
Predicative (before adjective or noun complement) — "is X"	Soft mutation (but NOT on ll-/rh-)	Mae'n ddiddorol (it is interesting)
Locative preposition (= "in")	Nasal mutation + yn → ym/yng	yng Nghaerdydd (in Cardiff)

Common mistake: treating progressive yn as if it mutates. Mae'n gadw is WRONG; Mae'n cadw is right. Verbal nouns after progressive yn keep their dictionary form.

1e. Possessive pronoun mutations (memorize this table)

Possessive	Meaning	Mutation triggered
fy	my	Nasal (fy nghar, fy mhen, fy nhad, fy ngardd, fy mrawd, fy nrws)
dy	your (ti, informal sg.)	Soft (dy gar, dy ben, dy dad, dy ardd, dy frawd, dy ddrws)
ei (masculine)	his	Soft (ei gar, ei ben, ei dad, ei ardd, ei frawd, ei ddrws)
ei (feminine)	her	Aspirate (ei char, ei phen, ei thad) — only c/p/t mutate
ein	our	NO mutation (ein car, ein pen, ein tad) — but often + "n" sandhi: ein nardd? No: ein gardd.
eich	your (chi, formal/plural)	NO mutation (eich car, eich pen, eich tad)
eu	their	NO mutation (eu car, eu pen, eu tad)

UI impact: Formal Welsh UI uses eich (no mutation) → simplifies translation. Informal UI uses dy + soft mutation → requires applying soft mutation to every possessed noun.

2. Welsh 29-Letter Alphabet — Digraphs Are Single Letters (severity 2.5)

The Welsh alphabet has 29 letters, including 8 digraphs that are treated as single letters for sorting, hyphenation, and counting:

a, b, c, ch, d, dd, e, f, ff, g, ng, h, i, j, l, ll, m, n, o, p, ph, r, rh, s, t, th, u, w, y

Critical: w and y are VOWELS in Welsh, not consonants. Welsh has 7 vowels: a, e, i, o, u, w, y. This is why words like cwm (valley), crwth (stringed instrument), y (the), bryn (hill) are valid — w and y are vowels carrying the syllable.

Digraph alphabetical order:

Digraph	Position	Example
ch	After c (NOT after h)	cae, ci, ciuto, ch-...
dd	After d	da, dy, ddim
ff	After f	ffon, ffeil
ng	After g (NOT between n and o!)	gan, gardd, ng-...
ll	After l	lle, llyfr
ph	After p	(rare outside mutations)
rh	After r	rhad, rhif
th	After t	thri, thal

Critical for sorting: Welsh dictionary order places ng after g, not between n and o. So nofio (to swim) comes BEFORE ngardd (my-garden), not after. Modern Welsh dictionaries follow this convention.

Critical for hyphenation: Never split a digraph. llygoden hyphenates as lly-go-den, never l-lygoden. anghofio hyphenates as ang-hof-io — no, actually an-gho-fio — wait, since ng is one letter, it stays together: a-ngho-fio. (Welsh hyphenation is complex; the rule is "treat digraphs as one letter".)

Critical for character counting: ffon (stick) has 3 letters (ff, o, n), not 4.

3. To Bach (Circumflex) — Long Vowels (severity 2.0)

The to bach ("little roof") is the circumflex accent that marks long vowels in Welsh. It appears on all 7 vowels: â, ê, î, ô, û, ŵ, ŷ.

The to bach is meaning-critical — it distinguishes minimal pairs:

Without to bach	Meaning	With to bach	Meaning
tan	until / fire	tân	fire (clarified)
gem	gem	gêm	game
ty	(no meaning alone)	tŷ	house
dyn	man	dŷn	(different sense)
llan	parish	llân	full
gwn	gun / I know (depends)	gŵn	gown / I know (different)
cyn	before	cŷn	chisel

Critical: ŵ and ŷ are uniquely Welsh letters. The circumflex on w and y appears in no other major Latin-script language. NEVER strip these to plain w and y — they change meaning.

Common UI words with to bach:

Welsh	Meaning
tŷ	house
tân	fire
cŵn	dogs (plural of ci)
gwŷr	husbands / men
ŵy	egg
ŷd	corn
â	with
ê	(interjection)

4. VSO Word Order (severity 2.0)

Welsh is strict VSO (verb-subject-object) in affirmative main clauses with inflected verbs. The verb comes FIRST.

✗ Wrong (English SVO)	✓ Correct (Welsh VSO)	Gloss
Y defnyddiwr cadwodd y ffeil	Cadwodd y defnyddiwr y ffeil	Saved-the-user-the-file (= The user saved the file)
Chi gallu newid gosodiadau	Gallwch chi newid gosodiadau	Can-you change settings
Y cyfrifiadur yn lawrlwytho	Mae'r cyfrifiadur yn lawrlwytho	Is-the-computer downloading
Y ci yn cysgu	Mae'r ci yn cysgu	Is-the-dog sleeping

Periphrastic constructions also follow VSO — the auxiliary bod (to be) is the verb:

English	Welsh
The user is saving the file.	Mae'r defnyddiwr yn cadw'r ffeil. (Is-the-user yn save-the-file)
The file has been saved.	Mae'r ffeil wedi'i chadw. (Is-the-file wedi-its saved [aspirate mutation on cadw → chadw because ffeil is feminine])
You can save your work.	Gallwch chi gadw eich gwaith. (Can-you save your work [cadw soft-mutates after the inflected modal gallwch])

5. Periphrastic Verb Constructions (severity 2.0)

Modern Welsh primarily uses periphrastic (auxiliary) verb constructions with bod (to be) + yn (progressive particle) + berfenw (verbal noun):

Tense	Pattern	Example
Present	Mae [subject] + yn + verbal noun	Mae e'n cadw (He is saving / He saves)
Past (continuous)	Roedd [subject] + yn + verbal noun	Roedd e'n cadw (He was saving)
Perfect	Mae [subject] + wedi + verbal noun (note: wedi replaces yn)	Mae e wedi cadw (He has saved)
Pluperfect	Roedd [subject] + wedi + verbal noun	Roedd e wedi cadw (He had saved)
Future	Bydd [subject] + yn + verbal noun	Bydd e'n cadw (He will save)
Conditional	Byddai [subject] + yn + verbal noun	Byddai e'n cadw (He would save)

Hard rules:

• ✗ Mae'n yn cadw — DOUBLE yn. Mae'n already contracts Mae + yn.
• ✗ Mae e wedi yn cadw — wedi REPLACES yn, not added to it.
• ✗ Mae'n gadw — progressive yn does NOT trigger mutation.
• ✓ Mae'n cadw — verbal noun stays in dictionary form after progressive yn.

6. Inflected Prepositions (severity 2.0)

Welsh prepositions conjugate for person and number. Unlike English (where prepositions are invariable: on me, on you, on him all use the same "on"), Welsh inflects the preposition itself.

Example: ar (on)

Person	Form	Meaning
1st sg.	arnaf fi / arna i	on me
2nd sg. (ti)	arnat ti	on you (ti)
3rd sg. m.	arno fe / arno fo	on him
3rd sg. f.	arni hi	on her
1st pl.	arnon ni	on us
2nd pl. / formal	arnoch chi	on you (chi)
3rd pl.	arnyn nhw	on them

Example: i (to)

Person	Form
1st sg.	i mi / i fi
2nd sg.	i ti
3rd sg. m.	iddo fe
3rd sg. f.	iddi hi
1st pl.	i ni
2nd pl.	i chi
3rd pl.	iddyn nhw

Example: gan (by / with possession) — also used to express HAVE in Welsh

Person	Form	Meaning
1st sg.	gen i / gennyf	by me / I have
2nd sg.	gen ti / gennyt	by you / you (ti) have
3rd sg. m.	ganddo fe / ganddo fo	by him / he has
3rd sg. f.	ganddi hi	by her / she has
1st pl.	gennyn ni / gennym ni	by us / we have
2nd pl.	gennych chi	by you (chi) / you have
3rd pl.	ganddyn nhw	by them / they have

Critical for UI:

• "You have 3 new files" = Mae gennych chi 3 ffeil newydd (formal) — NOT Mae chi 3 ffeil newydd.
• "Send it to me" = Anfonwch ef ataf fi — NOT Anfonwch ef i fi.
• "On your screen" = Ar eich sgrin — but "on me" pronouns require the inflected form arnaf fi.

7. Two-Gender System (severity 2.0)

Welsh has two grammatical genders: masculine (gwrywaidd) and feminine (benywaidd). About 60% of nouns are masculine.

Gender effects (the four things that change):

Effect	Masculine	Feminine
After definite article y	NO mutation: y car (the car)	SOFT mutation: y gath (the cat) ← cath
Adjective after singular noun	NO mutation: car mawr (big car)	SOFT mutation: cath fawr ← mawr (big cat)
Numeral form for 2	dau + soft: dau gar (two cars)	dwy + soft: dwy ferch (two girls)
Numeral form for 3	tri + aspirate: tri chi (three dogs)	tair (NO mutation): tair merch (three girls)
Numeral form for 4	pedwar + no mutation: pedwar ci	pedair + no mutation: pedair merch

Common UI-relevant noun genders:

Noun	Gender	Notes
ffeil (file)	Feminine	y ffeil, dwy ffeil
ffolder (folder)	Masculine	y ffolder, dau ffolder
cyfrifiadur (computer)	Masculine	y cyfrifiadur
gwefan (website)	Feminine	y wefan ← soft mut.
meddalwedd (software)	Feminine	y feddalwedd ← soft mut.
caledwedd (hardware)	Feminine	y galedwedd ← soft mut.
bysellfwrdd (keyboard)	Masculine	y bysellfwrdd
llygoden (mouse)	Feminine	y lygoden ← soft mut.
sgrin (screen)	Feminine	y sgrin (s- doesn't mutate)
gosodiad (setting)	Masculine	y gosodiad (sg.) / y gosodiadau (pl.)
defnyddiwr (user)	Masculine	y defnyddiwr
cyfrinair (password)	Masculine	y cyfrinair
cyfrif (account)	Masculine	y cyfrif
dolen (link)	Feminine	y ddolen ← soft mut.
iaith (language)	Feminine	yr iaith (vowel start → yr); tair iaith
dewis (choice)	Masculine	y dewis

Critical errors:

✗ Wrong	✓ Correct	Reason
y cath	y gath	cath is feminine → soft mutation after y
y ffeil mawr	y ffeil fawr	ffeil is feminine → adj. soft-mutates
dau ffeil	dwy ffeil	ffeil is feminine → use dwy not dau
dau ffeil	dwy ffeil + soft mutation (already in ffeil)	f- doesn't mutate but dwy requires soft mutation context
tri iaith	tair iaith	iaith is feminine → use tair
pedwar gwefan	pedair gwefan	gwefan is feminine → use pedair

8. Number System — Singular After Numerals 1-10 (severity 2.0)

Welsh uses singular noun forms after numbers 1-10, unlike English. For numbers 11+, the construction switches to o + plural (a partitive genitive structure).

Count	Pattern	Example
1	singular	un ffeil (one file)
2	dau/dwy + soft mut. + singular	dwy ffeil (two files)
3	tri/tair (+ aspirate for m.) + singular	tair ffeil (three files); tri chi (three dogs)
4	pedwar/pedair + singular	pedair ffeil (four files)
5	pump + singular	pump ffeil (five files) — sometimes pum (shortened form) before consonant
6	chwech + singular	chwe ffeil (six files) — chwe shortened; aspirate mut. on c/p/t
7	saith + singular	saith ffeil (seven files)
8	wyth + singular	wyth ffeil (eight files)
9	naw + singular	naw ffeil (nine files)
10	deg + singular	deg ffeil (ten files)
11+	numeral + o + plural	15 o ffeiliau (fifteen of files)

✗ Wrong (English-style plural)	✓ Correct (Welsh)
5 ffeiliau	5 ffeil
dau ffeiliau	dwy ffeil
3 ffeiliau	3 ffeil OR tair ffeil
10 ffeiliau	10 ffeil
15 ffeil	15 o ffeiliau
100 ffeil	100 o ffeiliau

Note on traditional vs modern (decimal) number system: Welsh historically uses a vigesimal (base-20) system: un ar bymtheg = 16 (one on fifteen), deugain = 40 (two-twenties), trigain = 60 (three-twenties). Modern Welsh, especially in UI and education, uses a decimal system: un deg chwech = 16 (one-ten-six), pedwar deg = 40. For UI work, prefer the decimal system — it's clearer and avoids confusion. Use Arabic numerals (16, 40) wherever practical to sidestep the issue.

9. Plural Formation — Six ICU Categories (severity 2.0)

Welsh has one of the most complex plural systems among European languages. ICU plural categories:

ICU category	Welsh count rule	Pattern	Example
zero (0)	dim + soft mutation + plural	dim + plural	dim ffeiliau (no files)
one (1)	singular, no mutation needed in many UI contexts	un + singular	1 ffeil / un ffeil
two (2)	dau/dwy + soft mut. + singular	dau/dwy + sg.	2 ffeil / dwy ffeil
few (3-6)	numeral + singular (gendered for 3,4)	tair/tri/pedair... + sg.	3 ffeil / tair ffeil
many (≥7 in some classes, often combined w/ "few")	numeral + singular	numeral + sg.	7 ffeil
other (11+, or default)	numeral + o + plural	15 o ffeiliau	15 o ffeiliau

Plural formation patterns (no single rule — each noun must be memorized):

Pattern	Singular	Plural
-au (most common)	ffeil	ffeiliau
-au	gosodiad	gosodiadau
-iau	drws	dryssiau (also: drysau)
-oedd	iaith	ieithoedd
-i	llyfr	llyfriau — actually llyfrau
-od	cath	cathod
-ed/-iaid	plentyn	plant (irreg.)
Vowel change	car	ceir
Vowel change	troed	traed
Vowel change	bachgen	bechgyn
Irregular	brawd	brodyr
Irregular	chwaer	chwiorydd
Irregular	dyn	dynion

There is no productive default plural ending — every Welsh noun's plural must be looked up.

UI plurals (memorize):

English	Singular	Plural
file	ffeil	ffeiliau
folder	ffolder	ffolderi / ffolderau
setting	gosodiad	gosodiadau
user	defnyddiwr	defnyddwyr
password	cyfrinair	cyfrineiriau
account	cyfrif	cyfrifon
computer	cyfrifiadur	cyfrifiaduron
website	gwefan	gwefannau
language	iaith	ieithoedd
choice	dewis	dewisiadau
link	dolen	dolenni
email	e-bost	e-byst / negeseuon e-bost

10. Adjective Placement — After the Noun (severity 1.5)

Most Welsh adjectives follow the noun (unlike English which puts them before):

✗ Wrong (English order)	✓ Correct (Welsh order)	Gloss
newydd ffeil	ffeil newydd	file new
mawr cyfrifiadur	cyfrifiadur mawr	computer big
cyflym cysylltiad	cysylltiad cyflym	connection fast

Adjectives that PRECEDE the noun (small closed class — and they trigger soft mutation):

Adjective	Meaning	Example
hen	old	hen dŷ (an old house) ← tŷ
prif	main, chief	y prif beth (the main thing) ← peth
unig	only, sole	yr unig ddefnyddiwr (the only user) ← defnyddiwr
holl	all, whole	yr holl ddefnyddwyr — actually yr holl ddefnyddwyr (all the users)
ambell	occasional, some	ambell ferch (some girl) ← merch
prin	scarce, rare	prin gi (a rare dog) ← ci

Feminine singular noun → adjective soft-mutates:

✗ Wrong	✓ Correct
merch tal	merch dal (← tal, soft mut. after fem. sg.)
cath mawr	cath fawr (← mawr)
ffeil newydd	ffeil newydd (n doesn't mutate, so no visible change)
gwefan da	gwefan dda (← da, soft mut.)

11. Definite Article y / yr / 'r — Forms by Context (severity 1.5)

Welsh has only ONE article — the definite article — which has three contextual forms:

Form	Use	Example
y	before consonants (default)	y car, y llyfr
yr	before vowels (a, e, i, o, u, w, y) and silent h	yr afon, yr iaith, yr heddlu
'r	after a vowel (in connected speech/writing)	Mae'r ffeil; o'r cyfrifiadur

There is NO indefinite article. ci means BOTH "dog" and "a dog" depending on context. Mae ci yma = "There is a dog here."

✗ Wrong	✓ Correct
y afon	yr afon (vowel start)
y iaith	yr iaith (vowel start)
Mae y ffeil	Mae'r ffeil (after vowel)
Aeth e i y siop	Aeth e i'r siop (after vowel)
yr car	y car (consonant start)

12. Possession by Juxtaposition (severity 2.0)

Welsh expresses possession by juxtaposition (placing nouns side by side), NOT with a preposition like English "of":

English	✗ Wrong (calque)	✓ Correct (Welsh)
John's car	car o John	car John
the user's file	y ffeil o'r defnyddiwr	ffeil y defnyddiwr
the file's name	yr enw o'r ffeil	enw'r ffeil
the user's password	cyfrinair o'r defnyddiwr	cyfrinair y defnyddiwr
the company's website	gwefan o'r cwmni	gwefan y cwmni
Wales's capital	prifddinas o Gymru	prifddinas Cymru

Pattern: [possessed thing] + [possessor], with the definite article (if any) placed only before the possessor: enw'r ffeil = "name [of] the file."

13. Aspirate Mutation on "a" (and) — Easy to Forget (severity 1.5)

The conjunction a ("and") triggers aspirate mutation on c, p, t. This is one of the most commonly missed mutations in Welsh writing.

✗ Wrong	✓ Correct
ffeil a cyfrif	ffeil a chyfrif (file and account)
dyn a plentyn	dyn a phlentyn (man and child)
coffi a tatws — te?	coffi a the (coffee and tea) ← well, te in Welsh; te + a = a the (aspirate)
Cymraeg a Saesneg	Cymraeg a Saesneg (s- doesn't mutate, OK)
llyfr a coffi	llyfr a choffi

Note: a becomes ac before vowels (and silent h): ffeil ac e-bost (file and email).

14. Welsh Quotation Marks (severity 1.0)

Welsh uses standard double quotes "..." (same as English).

"Croeso", meddai. — "Welcome," he said.

Single quotes '...' are used for nested quotes:

"Dywedodd, 'Croeso'", meddai. — "He said, 'Welcome',"  she said.

Some traditional Welsh typography uses guillemets «...» but this is rare in modern UI.

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UI Conventions

Buttons — Verbal Noun (Berfenw) — NOT Imperative

Welsh UI buttons use the berfenw (verbal noun) form — the dictionary form of the verb, functioning as an infinitive/gerund. This is the established Microsoft / Apple / LibreOffice / Welsh Government convention.

English	✓ Welsh button (berfenw)	✗ Wrong (imperative)
Save	Cadw	Cadwch / Cadwa
Cancel	Canslo	Canslwch
Delete	Dileu	Dilewch
Copy	Copïo	Copïwch
Paste	Gludo	Gludwch
Open	Agor	Agorwch
Close	Cau	Caewch
Edit	Golygu	Golygwch
Search	Chwilio	Chwiliwch
Send	Anfon	Anfonwch
Print	Argraffu	Argraffwch
Select	Dewis	Dewiswch
Continue	Parhau	Parhewch
Next	Nesaf / Ymlaen	—
Back	Yn ôl	—
Submit	Cyflwyno	Cyflwynwch
Confirm	Cadarnhau	Cadarnhewch
Done	Wedi gorffen / Gorffen	—
OK	Iawn / OK	—
Upload	Uwchlwytho	Uwchlwythwch
Download	Lawrlwytho	Lawrlwythwch
Refresh	Adnewyddu	—
Settings	Gosodiadau	—
Apply	Defnyddio / Cymhwyso	—
Reset	Ailosod	—
Add	Ychwanegu	—
Remove	Tynnu	—
Sign in / Log in	Mewngofnodi	—
Sign out / Log out	Allgofnodi	—
Sign up / Register	Cofrestru	—
Add more	Ychwanegu rhagor	— (use rhagor not mwy for buttons)
Show more	Dangos rhagor	—

Rationale: The berfenw (verbal noun) is register-neutral — it doesn't pick chi vs ti. This keeps button labels stable across formality levels.

Status Messages — Periphrastic with "Wrthi'n" or "Yn"

For in-progress states, use periphrastic constructions with bod + yn + verbal noun. For UI status messages specifically, Wrthi'n + verbal noun is the established pattern:

English	✗ Wrong (bare verbal noun)	✓ Correct (periphrastic)
Loading...	Llwytho...	Wrthi'n llwytho... / Yn llwytho...
Saving...	Cadw...	Wrthi'n cadw...
Sending...	Anfon...	Wrthi'n anfon...
Processing...	Prosesu...	Wrthi'n prosesu...
Connecting...	Cysylltu...	Wrthi'n cysylltu...
Searching...	Chwilio...	Wrthi'n chwilio...
Translating...	Cyfieithu...	Wrthi'n cyfieithu...
Downloading...	Lawrlwytho...	Wrthi'n lawrlwytho...
Uploading...	Uwchlwytho...	Wrthi'n uwchlwytho...
Please wait	—	Arhoswch / Os gwelwch yn dda, arhoswch

Completion Messages — Impersonal Past or "Wedi'i" Construction

For completed states, use either the impersonal past (-wyd ending) or the wedi'i + soft-mutated verbal noun construction:

English	✗ Wrong	✓ Correct
Saved	Cadw	Cadwyd / Wedi'i gadw (soft mut. — cadw → gadw)
Sent	Anfon	Anfonwyd / Wedi'i anfon
Deleted	Dileu	Dilëwyd / Wedi'i ddileu (soft mut.)
Done	Wedi gorffen	Wedi gorffen / Wedi cwblhau
Translation complete	Cwblhau cyfieithu	Cyfieithiad wedi'i gwblhau / Cwblhawyd y cyfieithiad
File uploaded	Uwchlwythwyd ffeil	Uwchlwythwyd y ffeil / Ffeil wedi'i huwchlwytho
Payment successful	Llwyddiant taliad	Taliad llwyddiannus / Talwyd yn llwyddiannus

Failure Messages — Impersonal Negative or "Heb"

For failure / error states:

English	✓ Welsh
Failed	Methwyd / Ni lwyddwyd
Could not save	Ni lwyddwyd i gadw (NOT Methodd cadw)
File not found	Ni ddaethpwyd o hyd i'r ffeil / Ffeil heb ei chanfod
Not saved	Heb ei gadw (without its-being-saved)
Connection lost	Collwyd y cysylltiad

Empty States — Dim or Heb

For empty states:

English	✓ Welsh
No results	Dim canlyniadau
No files	Dim ffeiliau
Nothing selected	Dim wedi'i ddewis / Heb ddewis dim
No notifications	Dim hysbysiadau
Empty	Gwag

Drag-and-Drop

• drag → llusgo (native Welsh — NOT dragio)
• drop / release → gollwng (native Welsh — NOT rhyddhau which means "liberate")

English	✓ Welsh
Drag files here	Llusgwch ffeiliau yma
Drop to upload	Gollwng i uwchlwytho
Release to upload	Gollwng i uwchlwytho (NOT Rhyddhau i uwchlwytho)

File Picker — Dewis not Pori

For file selection, use the action-oriented verb dewis (select/choose), NOT the navigation verb pori (browse):

✗ Wrong	✓ Correct
Pori am ffeiliau	Dewis ffeiliau
Cliciwch i bori	Cliciwch i ddewis (note soft mut. on dewis after i)
Pori	Dewis ffeil / Dewis

"More" — Rhagor not Mwy (for buttons)

For button idioms expressing "more", rhagor is more natural and formal than mwy in UI:

✗ Less natural	✓ More natural
Ychwanegu mwy	Ychwanegu rhagor
Dangos mwy	Dangos rhagor
Llwytho mwy	Llwytho rhagor

Error Messages — What + Next Step

Welsh UI errors follow the pattern what went wrong + what to do next:

✗ Bare	✓ With next step
Ffeil heb ei chanfod.	Ffeil heb ei chanfod. Gwiriwch y llwybr. (File not found. Check the path.)
Gwall rhwydwaith.	Gwall rhwydwaith. Rhowch gynnig arall. (Network error. Try again.)
Cyfrinair anghywir.	Cyfrinair anghywir. Ceisiwch eto. (Wrong password. Try again.)

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Punctuation, Numbers, Dates, Currency

Punctuation

Mark	Welsh	Notes
Question mark	?	Same as English
Comma	,	Different conjunction rules — see below
Period	.	Same
Colon	:	Same
Quotation marks	"..." (standard)	Same as English
Nested quotes	'...'	Single inside double
Apostrophe	'	Used in contractions (Mae'r, o'r, i'r)

Comma Rules

Rule	Example
NO comma before a / ac (and)	Llyfr a cherdyn (book and card) — NOT Llyfr, a cherdyn.
NO comma before neu (or)	Ffeil neu ffolder — NOT Ffeil, neu ffolder.
Comma before bod (that, subordinating)	Gwn**,** bod y ffeil yn gywir.
Comma before os (if)	Cadwch y ffeil**,** os ydych yn barod.
Comma before pan (when)	Anfonwch e-bost**,** pan fyddwch yn barod.
Comma before achos / oherwydd (because)	Methodd**,** oherwydd gwall rhwydwaith.
Comma before ond (but)	Cyflym**,** ond dibynadwy.

Numbers

Welsh follows UK / Anglo number formatting (not continental European):

Format	Pattern	Example
Thousands separator	comma (,)	1,234,567
Decimal separator	period (.)	3.14 / 99.99
Negative	-25
Percent	25% or 25 %

✗ Wrong (continental)	✓ Correct (Welsh/UK)
1.234,56	1,234.56
3,14	3.14
1 234	1,234

Dates

Format	Example	Use
DD/MM/YYYY	15/01/2024	Default Welsh format (UK convention)
D Month YYYY	15 Ionawr 2024	Long-form prose
D'ed/-fed Month YYYY	15fed Ionawr 2024	With ordinal suffix (more formal)
YYYY-MM-DD	2024-01-15	Technical/API only

Welsh month names (CAPITALIZED):

#	Welsh
1	Ionawr
2	Chwefror
3	Mawrth
4	Ebrill
5	Mai
6	Mehefin
7	Gorffennaf
8	Awst
9	Medi
10	Hydref
11	Tachwedd
12	Rhagfyr

Welsh weekday names (lowercase in the format dydd X):

Day	Welsh
Monday	dydd Llun
Tuesday	dydd Mawrth
Wednesday	dydd Mercher
Thursday	dydd Iau
Friday	dydd Gwener
Saturday	dydd Sadwrn
Sunday	dydd Sul

Note: dydd (day) is lowercase; the day name itself is capitalized (e.g., dydd Llun). Week starts Monday.

Time

• 24-hour preferred: 14:30.
• 12-hour with y.b. (yn y bore = a.m.) / y.p. (yn y prynhawn = p.m.) / y.h. (yn yr hwyr = evening): 2:30 y.p.

Currency — GBP (£) — Wales Uses British Pound

Format	Pattern	Example
Symbol before amount	£	£99.99
With pence	period decimal	£99.99 (not £99,99)
ISO code	GBP	99.99 GBP
Large amounts	comma thousands	£1,234.56

Wales is part of the United Kingdom and uses the British pound sterling (£, GBP). Wales does NOT use the euro. Penny/pence are subdivisions: 100 pence = £1.

Welsh words:

• pound = punt (plural: punnoedd / punt)
• pence = ceiniog (plural: ceiniogau)
• £99.99 = "naw deg naw punt naw deg naw ceiniog" (literal) — but in UI just write £99.99.

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Terminology — Welsh Native Terms (Established UI Vocabulary)

Welsh has an active terminology coordination effort — primarily through BydTermCymru (the National Terminology Portal of the Welsh Government) and Y Termiadur Addysg (the educational terminology standard). For UI work, use established Welsh terms:

English	✓ Welsh (preferred)	✗ Avoid (anglicism)	Notes
save	cadw	seifio	"to keep" — native verb
delete	dileu	deletio	native verb
copy	copïo	—	accepted Welsh form of borrowed verb
paste	gludo	pestio	"to stick" — native
cut	torri	cytio	"to cut/break" — native
open	agor	opnio	native
close	cau	clôsio	native
file	ffeil	—	borrowed but Welshified
folder	ffolder	—	borrowed but accepted
settings	gosodiadau	settings	native plural
upload	uwchlwytho	uploadio	"load upwards" — native compound
download	lawrlwytho	downloadio	"load downwards" — native compound
search	chwilio	sêrtsio	native
click	clicio	—	accepted borrowing
computer	cyfrifiadur	compiwtar	"calculator" — native coinage
software	meddalwedd	software	"soft-ware" calque, native
hardware	caledwedd	hardware	"hard-ware" calque, native
internet	rhyngrwyd	internet (also OK)	"inter-net" — native calque
browser	porwr	browser	"grazer" — native
website	gwefan	website	"web-place" — native
email	e-bost	email	"e-post" — native
password	cyfrinair	password	"secret-word" — native
user	defnyddiwr	user	native; pl. defnyddwyr
account	cyfrif	account	"calculation/count" — native
log in	mewngofnodi	logio	"log-in" — native compound
log out	allgofnodi	logio allan	"log-out" — native
cancel	canslo	—	accepted borrowing
print	argraffu	—	native
send	anfon	—	native
select	dewis	selectio	native (also "choice")
dashboard	dangosfwrdd	dashboard	"show-board" — native
app / application	ap (informal) / rhaglen (formal)	—	both accepted
link	dolen	link	"loop" — native
menu	dewislen	menu	"choice-page" — native
screen	sgrin	—	accepted borrowing
keyboard	bysellfwrdd	keyboard	"keys-board" — native
mouse	llygoden	mouse	"mouse" — native (same animal)
icon	eicon	—	accepted borrowing
error	gwall	error	native
warning	rhybudd	warning	native
help	help / cymorth	—	both used
support	cefnogaeth	support	native
feedback	adborth	feedback	"echo-talk" — native
privacy	preifatrwydd	privacy	native
terms	telerau	terms	native
language	iaith (sg.) / ieithoedd (pl.)	—	native
color	lliw	colour	native
size	maint	size	native
font	ffont	—	accepted borrowing
update (v.)	diweddaru	updatio	"to date-up" — native
share	rhannu	—	"to share/divide" — native
profile	proffil	—	accepted borrowing
notifications	hysbysiadau	notifications	"announcements" — native
home	hafan	home	"haven/home" — native
URL	URL / gwe-gyfeiriad	—	URL acceptable in tech contexts
WiFi	WiFi / diwifr	—	WiFi acceptable
device	dyfais	device	"invention" — native
video	fideo	—	accepted borrowing
photo	llun / ffotograff	—	both used
sync	cysoni	—	"to harmonize" — native
build (sw.)	adeiladu	—	native
deploy	defnyddio / gosod	—	native
log (n.)	cofnod / cofnodion	—	native

Brand Names and Tech Identifiers — Keep As-Is

Inside Welsh text, these stay in English / Latin:

• Brand names: Google, Microsoft, Apple, GitHub, Facebook, Twitter
• Tech identifiers: Git, Docker, npm, pip, HTTP, REST, JSON, XML, API, URL
• Codes/commands/paths: command names, file paths, code samples
• Placeholders: {name}, {count}, %s

Critical: do NOT mutate brand names. Even when grammatical context would normally trigger a mutation, brand names stay exactly as the brand spells them:

✗ Wrong (mutated)	✓ Correct (preserved)
Gyda Google (should soft mut. G → ∅?)	Gyda Google
O Facebook	O Facebook
Yn Ngoogle	Yn Google

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Calque / Anti-Pattern Blocklist (Avoid English Calques)

Welsh-language identity is culturally important. Calques (literal translations) from English read as lazy or anglicized. Replace them with native Welsh expressions:

✗ English calque	✓ Native Welsh	Note
Ar ddiwedd y dydd (at the end of the day)	Yn y pen draw / Wedi'r cwbl	English idiom calque
Gwneud synnwyr (makes sense)	Bod yn synhwyrol / Mae'n gwneud sens (colloquial OK)	"Makes sense" calque
Ar yr un dudalen (on the same page)	Yn cytuno / O'r un farn	"Same page" calque
Torri coes (break a leg)	Pob lwc! / Dal ati!	Use native good-luck idiom
Darn o gacen (piece of cake)	Hawdd fel baw / Dim problem	Use native easy idiom
Mae'n cymryd lle (it takes place)	Mae'n digwydd / Mae'n cael ei gynnal	"Take place" calque — use digwydd
Mae e wedi mynd yn ôl ar ei air (gone back on his word)	Mae e wedi torri ei air	Use native idiom
Yn seiliedig ar (based on — as sentence opener)	Ar sail / Yn ôl	Verbose calque
Er mwyn i (in order to)	Er mwyn / I	Verbose — short form suffices
actwali	mewn gwirionedd / a dweud y gwir	Anglicism — use native
siŵr (informal for "sure")	sicr / pendant (in formal UI)	siŵr is OK colloquially but use sicr in UI
jyst	dim ond / yn unig	Anglicism — use native
rili (really)	mewn gwirionedd / iawn	Anglicism
OK (in body text)	Iawn / O'r gorau	Use native (OK accepted in buttons)
AI-yredig ("AI-driven" calque)	gyda chymorth AI / wedi'i bweru gan AI	Compound-adjective calque
X-bwerus ("X-powered" suffix)	wedi'i bweru gan X	Compound suffix calque
Gwneud cyfraniad (make a contribution)	Cyfrannu	Use verb, not "make + noun"
Gwneud penderfyniad (make a decision)	Penderfynu	Use verb
Cael profiad (have an experience)	Profi	Use verb
Y ffeil ddim gallu bod wedi'i ffeindio	Ni ddaethpwyd o hyd i'r ffeil / Ffeil heb ei chanfod	Passive construction calque
Unol Daleithiau America (in UI body)	UDA	Use abbreviation in UI

Compound Adjective Calques (avoid)

English compound adjectives like AI-powered, cloud-based, data-driven do NOT calque well into Welsh. Restructure:

✗ Calque	✓ Welsh natural
AI-yredig	gyda chymorth AI / wedi'i bweru gan AI / yn defnyddio AI
cloud-based	yn seiliedig ar y cwmwl / wedi'i seilio ar y cwmwl
data-driven	wedi'i yrru gan ddata / yn seiliedig ar ddata
user-friendly	hawdd ei ddefnyddio ("easy to use")
AI-powered	wedi'i bweru gan AI

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Self-Check Checklist (Run Before Returning Output)

Identity (auto-fail on miss)

• Output is Welsh (Cymraeg), NOT Irish/Gaelic, NOT English.
• No Gaelic vocabulary (no Sláinte, Fáilte, Slán).
• Welsh letters used: w, y, ŵ, ŷ, â, ê, î, ô, û.
• No grave accents (Welsh uses circumflex, never grave).

Mutations (auto-fail)

• Soft mutation applied after: dy, ei (his), y (before fem. sg.), i, o, am, ar, at, gan, dros, drwy, wrth, neu (sometimes), yn (adverbial/predicative), dau/dwy, prif/hen/unig/holl.
• Nasal mutation applied after: fy, yn (locative — "in" + place).
• Aspirate mutation applied after: ei (her), a (and), â (with), gyda, tri, chwe, tua.
• No mutation after: ein, eich, eu, yn (progressive — before verbal noun).
• Direct object of inflected (conjugated) verb is soft-mutated.
• Adjective after feminine singular noun is soft-mutated.

Welsh Alphabet & Spelling (auto-fail)

• Digraphs (ch, dd, ff, ng, ll, ph, rh, th) treated as single letters — not split.
• To bach (â ê î ô û ŵ ŷ) preserved where meaning-critical (tŷ, cŵn, ŵy).
• ŵ and ŷ (uniquely Welsh) preserved — not stripped to plain w/y.
• No ASCII-stripping of accents.

Word Order (auto-fail)

• VSO in main clauses — verb first (Cadwodd y defnyddiwr y ffeil).
• Periphrastic constructions use bod + yn + berfenw (Mae'n cadw).
• Subject does NOT precede the verb in main clauses.

Articles & Possession

• Definite article correct: y (before consonants), yr (before vowels/h), 'r (after vowel).
• No indefinite article (don't insert "a" or "an" calque).
• Possession by juxtaposition (car John, not car o John).

Pronouns & Register

• chi / ti consistent throughout — never mix.
• If chi: eich (no mutation), -wch imperatives.
• If ti: dy (+ soft mutation), -a imperatives.
• Buttons use berfenw (Cadw, Dileu — register-neutral).
• Inflected prepositions used correctly (arnaf fi, iddi hi, ganddyn nhw).

Gender & Number

• Gender correct on nouns (ffeil = f., cyfrifiadur = m., gwefan = f.).
• Feminine sg. noun soft-mutates after y AND triggers soft mutation on following adjective.
• dau / dwy, tri / tair, pedwar / pedair match noun gender.
• Singular noun after numerals 1-10 (5 ffeil, not 5 ffeiliau).
• "o" + plural for numerals 11+ (15 o ffeiliau).
• Plural form correct per noun (ffeil → ffeiliau, iaith → ieithoedd, dyn → dynion).

Verbs

• Periphrastic bod + yn + berfenw for present/past continuous.
• wedi (perfect) REPLACES yn, not added to it.
• No double yn (Mae'n yn cadw ✗ → Mae'n cadw ✓).
• Impersonal past -wyd for completion (Cadwyd, Anfonwyd).
• "Wedi'i" + soft-mutated berfenw for completion alternative (Wedi'i gadw).
• "Heb" + soft-mutated berfenw for negation (Heb ei gadw).
• "Ni lwyddwyd i" + berfenw for failure (Ni lwyddwyd i gadw).

UI Conventions

• Buttons in berfenw (Cadw, Dileu, Copïo, Agor).
• Status messages with Wrthi'n + berfenw (Wrthi'n cadw...).
• Completion with impersonal past or Wedi'i + soft-mut. berfenw.
• Drag-and-drop: llusgo / gollwng (not dragio / rhyddhau).
• File picker: dewis (not pori).
• "More" buttons: rhagor (not mwy).
• Empty states: Dim X / Heb ddim.
• Error messages include next step.

Punctuation & Numbers

• Decimal: period (3.14).
• Thousands: comma (1,234).
• NO comma before a / ac / neu.
• Comma before bod / os / pan / oherwydd / ond.
• Quotation marks: "..." (standard, same as English).

Dates & Currency

• DD/MM/YYYY date format (UK convention).
• Months capitalized: Ionawr, Chwefror, Mawrth, Ebrill, Mai, Mehefin, Gorffennaf, Awst, Medi, Hydref, Tachwedd, Rhagfyr.
• Days lowercase with dydd: dydd Llun, dydd Mawrth....
• GBP £ currency, NOT EUR (Wales uses British pound).
• Period decimal on currency: £99.99, not £99,99.

Terminology

• Native Welsh terms used: cadw, dileu, lawrlwytho, uwchlwytho, cyfrifiadur, meddalwedd, cyfrinair, defnyddiwr, gosodiadau.
• No anglicism-verbs (no seifio, deletio, downloadio, uploadio).
• Brand names unchanged (Google, NOT mutated).
• No English plurals (no ffeils; use ffeiliau).

Calques

• No "make + noun" calques (use the verb: Cyfrannu, not Gwneud cyfraniad).
• No "at the end of the day" calque (use Yn y pen draw).
• No "X-powered" compound-adj calques (use wedi'i bweru gan X).
• No passive-voice English calques (use Welsh impersonal -wyd).

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Worked Examples

Example 1 — Standard cy UI (chi formal)

Source (neutral product UI):

Welcome back! You have 3 new files in your account. Click Continue to review them or Cancel to stay here. Saving your changes…

Register check: professional product UI → chi formal, native Welsh vocabulary, berfenw buttons.

Translation:

Croeso 'nôl! Mae gennych chi 3 ffeil newydd yn eich cyfrif. Cliciwch ar Parhau i'w hadolygu neu Canslo i aros yma. Wrthi'n cadw eich newidiadau…

Why this works:

• Croeso 'nôl — "Welcome back" (native idiom; 'nôl is contracted yn ôl).
• Mae gennych chi — "Have you" — uses inflected preposition gennych (gan conjugated for chi). Welsh expresses HAVE with gan + person.
• 3 ffeil newydd — singular ffeil after numeral (per Welsh number rule); newydd follows the noun (post-nominal adjective). No mutation needed because ffeil is feminine but newydd starts with n which doesn't mutate.
• yn eich cyfrif — "in your account": yn here is the predicative/locative use (no mutation needed because we're treating it as connector with possessive eich which itself takes no mutation). cyfrif is masculine.
• Cliciwch ar Parhau — chi-form imperative Cliciwch (-wch ending); ar governs subsequent noun; Parhau is the button label (berfenw, register-neutral).
• i'w hadolygu — "to review them": i + eu (their) → i'w; adolygu takes h- before vowel-starting verbal noun when preceded by certain particles (specifically ei/eu in 3rd person object construction).
• neu Canslo — "or Cancel": neu (or) takes no mutation in modern Welsh.
• i aros yma — "to stay here": aros (to wait/stay) is the berfenw; yma (here).
• Wrthi'n cadw eich newidiadau… — status message in periphrastic form. Wrthi'n = "in the act of"; cadw = berfenw (no mutation after progressive yn); eich newidiadau = "your changes" (no mutation after eich).
• All to bach (none in this text) and digraphs (ch in cliciwch, adolygu) preserved.

Example 2 — Mutation Showcase

Source: I saw my dog and her cat in Cardiff.

Translation:

Gwelais fy nghi a'i chath yng Nghaerdydd.

Mutation analysis:

• fy nghi — "my dog": fy triggers nasal mutation on ci → nghi.
• a'i — "and her": a + ei (her) → a'i (contracted).
• chath — "cat" after ei (her) → aspirate mutation cath → chath.
• yng Nghaerdydd — "in Cardiff": yn (locative) triggers nasal mutation on Caerdydd → Nghaerdydd; yn itself becomes yng before ng-/ngh-.
• Gwelais — 1st sg. past of gweld (to see); inflected verb form (not periphrastic).

This single sentence demonstrates all three mutation systems and the yn → yng sandhi change.

Example 3 — Periphrastic Verb Constructions

Source: The user is downloading the file. The file has been saved.

Translation:

Mae'r defnyddiwr yn lawrlwytho'r ffeil. Mae'r ffeil wedi'i chadw.

Analysis:

• Mae'r defnyddiwr — "Is-the-user" — VSO with auxiliary bod; Mae + yr → Mae'r.
• yn lawrlwytho — progressive yn + verbal noun lawrlwytho; NO mutation (progressive yn never mutates).
• 'r ffeil — "the file" (definite article 'r after vowel of lawrlwytho).
• Mae'r ffeil wedi'i chadw — "Is-the-file having-its saved": perfect aspect uses wedi + ei (its, referring back to ffeil feminine) + soft-mutated verbal noun. ffeil is feminine, so ei (her/its-fem.) triggers aspirate mutation on cadw → chadw.

Wait — ei for feminine triggers aspirate, but for masculine triggers soft. cadw starts with c. Aspirate of c is ch. So wedi'i chadw is correct here (because ffeil is feminine).

If the subject were masculine (e.g., cyfrif = account, masc.): Mae'r cyfrif wedi'i gadw (soft mutation c → g).

Example 4 — VSO with Inflected vs Periphrastic Verbs

Source (with inflected verb — past): The user saved the file.

Cadwodd y defnyddiwr y ffeil.

• Cadwodd — 3rd sg. past of cadw (inflected). Comes FIRST (VSO).
• y defnyddiwr — subject (definite article + noun).
• y ffeil — direct object. Direct object after inflected verb takes soft mutation if the object starts with a mutable consonant — but ffeil starts with ff which doesn't soft-mutate (ff is already in the mutated form of p; ff doesn't further mutate to anything in soft mutation).

Source (periphrastic — present continuous): The user is saving the file.

Mae'r defnyddiwr yn cadw'r ffeil.

• Mae — 3rd sg. of bod (to be).
• 'r defnyddiwr — subject.
• yn cadw — progressive yn + berfenw cadw (no mutation).
• 'r ffeil — direct object (no mutation in periphrastic — object mutation rule only applies to direct objects of INFLECTED verbs, not periphrastic).

Example 5 — Anglicism Rejection

Source: Click here to download the software update.

✗ Wrong (anglicism-heavy):

Clicia yma i downloadio'r software update.

✓ Correct (native Welsh):

Cliciwch yma i lawrlwytho'r diweddariad meddalwedd.

Notes:

• downloadio → lawrlwytho ✓ (native)
• software → meddalwedd ✓ (native)
• update (n.) → diweddariad ✓ (native, from diweddaru = to update)
• i lawrlwytho — i (to) triggers soft mutation: lawrlwytho (no visible change because l → l, but mutation rule applies).
• 'r diweddariad meddalwedd — possession by juxtaposition: "the update [of] software" → diweddariad meddalwedd (no preposition).

Example 6 — Currency (GBP)

Source: Subscription: £9.99 / month.

Translation:

Tanysgrifiad: £9.99 y mis.

• Tanysgrifiad — "subscription" (native).
• £9.99 — UK number format (period decimal). Welsh follows Anglo convention.
• y mis — "the month" — Welsh uses y before the time unit for periodic charges.

Example 7 — Inflected Prepositions in Action

Source: Send the file to me. Show it to her.

Translation:

Anfonwch y ffeil ata i. Dangoswch hi iddi hi.

• Anfonwch — chi imperative of anfon (send).
• ata i — inflected form of at (towards) for 1st sg.: at + fi → ata i.
• Dangoswch hi — chi imperative + hi (it-fem., referring to ffeil which is feminine).
• iddi hi — inflected form of i (to) for 3rd sg. fem.: i + hi → iddi hi.

Example 8 — Numbers with Gender

Source: 2 dogs, 2 cats, 3 files, 3 men.

Translation:

dau gi, dwy gath, tair ffeil, tri dyn.

• dau gi — ci (dog) is masc. → dau + soft mut. ci → gi.
• dwy gath — cath (cat) is fem. → dwy + soft mut. cath → gath.
• tair ffeil — ffeil is fem. → tair (fem. form of three); ff doesn't aspirate-mutate.
• tri dyn — dyn (man) is masc. → tri (masc. form); d doesn't aspirate-mutate (only c/p/t aspirate-mutate, but tri triggers aspirate only on c/p/t — d is unaffected).

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When in Doubt

1. Default to cy / Welsh standard written, chi formal register, native Welsh vocabulary, berfenw buttons, DD/MM/YYYY dates, GBP £ currency (1,234.56 format).
2. Check mutations first — if the source has a word like fy / dy / ei / y / a / yn / o / i / am / ar, the next word probably mutates. Confirm: soft / nasal / aspirate?
3. VSO — if you wrote Y defnyddiwr cadwodd, restructure to Cadwodd y defnyddiwr.
4. No indefinite article — don't translate English "a/an" as a word; just omit.
5. Possession by juxtaposition — don't insert o between possessed and possessor: car John, not car o John.
6. Inflected prepositions — if pronoun follows preposition, use the conjugated form (arnaf fi, iddi hi, ganddyn nhw), not bare preposition + pronoun.
7. Periphrastic verbs — for present/past continuous, use bod + yn + berfenw (Mae'n cadw, Roedd e'n cadw). Never double yn. wedi replaces yn for perfect aspect.
8. Numbers — singular noun after 1-10, o + plural for 11+. dau/dwy, tri/tair, pedwar/pedair must match gender.
9. Gender — if you don't know a noun's gender, look it up. Get it wrong and adjectives + articles will be wrong too.
10. chi/ti consistency — pick one register and stick with it throughout. Buttons use berfenw (neutral).
11. Buttons use berfenw, NOT imperative — Cadw, not Cadwch. This is the established Welsh software convention.
12. Status messages — Wrthi'n + berfenw (in-progress), impersonal -wyd past (completed).
13. Anglicisms — if you wrote seifio, deletio, downloadio, uploadio, fix to cadw, dileu, lawrlwytho, uwchlwytho.
14. To bach (circumflex) — preserve on long vowels; tŷ (house), cŵn (dogs), gŵr (husband/man). Never strip to plain ty, cwn, gwr.
15. Digraphs are single letters — ch, dd, ff, ng, ll, ph, rh, th. Don't split them in hyphenation; don't sort them as two letters.
16. Currency is £ GBP, not € EUR — Wales uses British pound.
17. Brand names don't mutate — gyda Google, not gyda Oogle; o Facebook, not o Vacebook.
18. If you're unsure about a mutation, ask: "what's the trigger word?" — Then look up which mutation that trigger requires. The trigger determines the mutation, not the mutating word itself.
19. Reference official terminology: BydTermCymru (https://termau.cymru/) and Y Termiadur Addysg for established Welsh tech terms.
20. Cymraeg Clir — favor clear, accessible Welsh in UI. Avoid archaic or overly literary forms unless the context calls for them.