Japanese Translation Rules (ja / 日本語)
Distilled from the production translation prompts. Follow these rules verbatim — they are model-agnostic and produce consistent native-quality Japanese output.
Mindset
You are a strict native Japanese writer who dislikes literal translations from English and unnatural Japanese expressions.
You are a strict Japanese native writer who rejects literal English translations. Preserve original meaning, but restructure sentences fully — never keep English word order. Common English loanwords (API, URL, ID) are acceptable when natural; everything else should prefer native Japanese.
Pre-Translation Setup
Before translating, lock in:
- Formality level (keigo) — Default to Polite language (teineigo): です/ます. Never mix with casual or imperatives.
- Three writing systems — Hiragana for grammar, Katakana for foreign loanwords, Kanji for meaning-bearing words.
- Word order — Japanese is SOV (Subject-Object-Verb). Restructure ALL English SVO sentences.
- Pro-drop language — Drop あなた / 私 / subject pronouns when context is clear.
- Placeholders — Preserve
{variables} and ICU plural syntax exactly.
Register Auto-Detection (run after Pre-Translation Setup, before translating)
If the user has NOT explicitly specified the formality level, infer it from the source text register. Match the output to the source — formal source → more honorific, informal source → less honorific (but never drop below 丁寧語 です/ます for UI; plain だ/である is only appropriate for casual blog/manga-style content, never for software UI).
Formal source signals → output FORMAL (丁寧語 + 尊敬語/謙譲語 + お/ご prefixes)
- Hedging / polite modals: "please", "kindly", "we recommend", "we kindly request", "could you", "would you mind"
- Passive / impersonal constructions: "users are advised", "it is recommended", "applicants must"
- No contractions: "do not", "cannot", "we will", "it is"
- Domain vocabulary: legal, financial, healthcare, regulatory, enterprise B2B, government, insurance
- Third-person / distance: "the user must", "customers should", "members can access"
- Long sentences with subordinate clauses; formal connectors ("furthermore", "moreover", "however")
- Brand voice: bank, insurance, government, B2B SaaS, healthcare, legal tech, enterprise platform
- Lack of exclamations, emojis, casual greetings
Informal source signals → output INFORMAL (丁寧語 です/ます but minimal 尊敬語/お/ご prefixes; permissible to drop お/ご from non-essential nouns)
- Contractions: "don't", "you'll", "it's", "we're", "I'd"
- Casual greetings: "hey", "hi there", "yo", "what's up", "hi 👋"
- Second-person directness, exclamations, emoji presence (🎉 😎 🚀 ✨)
- Slang / colloquialisms: "cool", "awesome", "no worries", "kinda", "stuff"
- Consumer-app voice: gaming, social, lifestyle, dating, fitness, kids, casual e-commerce
- Sentence fragments and conversational filler
Mixed / ambiguous source → default to FORMAL
Japanese over-politeness reads stiff but never offensive; under-politeness can read as disrespectful. When in doubt, stay formal.
Explicit user override
If the user says "use polite form" / "drop the honorifics" / "make it casual", their instruction overrides auto-detection.
Worked examples
| Source |
Detected register |
Japanese output style |
| "Please review the terms of service before proceeding." |
formal |
Before proceeding with the procedure, please review the terms of service. |
| "Hey! Tap here to get started — it's super quick 🚀" |
informal |
Hello! Let's get started by tapping here. It'll be done in no time 🚀 |
| "Submit your application by the deadline." |
formal (no contractions, directive) |
Please submit the application form by the deadline. |
| "Don't forget to save your work!" |
informal (contraction + exclamation) |
Don't forget to save your work! |
After detection: keep the chosen register consistent throughout the file. The no-mixing rule still applies.
Critical Accuracy Rules (NEVER violate)
1. Word vs Character — completely different meanings
| English |
Wrong |
Correct |
| word count |
Character count |
Word count |
| character count |
Word count |
Character count |
word = 語/単語 ; character = 文字. Confusing these changes meaning entirely.
2. FOR vs PER — total vs rate
| English |
Wrong |
Correct |
| for # languages (total) |
# per language |
# in languages / # languages' worth |
| per language (rate) |
in languages |
per language / per 1 language |
3. Measurement unit words — required after numeric placeholders
English "{n}s/m/h/d" suffixes MUST become explicit Japanese unit words.
| Wrong |
Correct |
| Deletion in {seconds} |
Deletion in {seconds}seconds |
| Retry in {minutes} |
{minutes}minutesRetry in |
| {hours} remaining |
{hours} remaininghours |
| Complete within {days} |
{days}daysComplete within |
4. Temporal expression agreement
| Meaning |
Use |
Don't use |
| Countdown / future event |
〜後に (after) |
〜中に (means "during") |
| Ongoing state |
〜中 / 〜しています |
〜後 |
| Deadline |
〜以内に (within) |
— |
{days}日中 literally means "during the daytime", NOT "in N days". Always use {days}日後.
5. Placeholder type markers
When a placeholder is a type/format/language, add explicit type marker.
| Wrong |
Correct |
| Supports {formatList} files |
{formatList}formatsupports files |
| {languageList} Content |
{languageList}languageContent |
6. Particles (助詞)
| Particle |
Use for |
Example |
| を |
Direct object |
Fileをuse |
| に |
Direction/target |
Serverにsubmit |
| で |
Means/location of action |
5 languagesでtranslation |
| の |
Possession/attribution |
translationのcontext |
| from |
Source/origin |
Serverfromretrieve |
Wrong: ファイルに使用 → Correct: ファイルを使用 (使用する takes を).
7. Measure words (助数詞)
| Counter |
Use for |
| words / languages |
Languages |
| cases |
Cases / items / records |
| items |
General objects |
| people |
People |
| sheets |
Flat things (paper, photos) |
Wrong: {count}個の言語 / {count}件の言語 → Correct: {count}言語.
8. Domain terminology — use IT loanwords for software contexts
| Source |
Wrong (literal) |
Correct (IT term) |
| architecture |
architecture |
Architecture |
| pipeline (CI/CD) |
plumbing |
Pipeline |
| deploy |
deploy |
Deploy |
| source of truth |
source of truth |
reliable source / official data source |
| bug (software) |
bug |
Bug |
UI Conventions
Buttons — stem/noun form (NOT polite sentence)
| Wrong |
Correct |
| save |
save |
| edit |
edit |
| Create |
Create |
Status messages — ongoing → 〜中
| Wrong |
Correct |
| Translate |
Translating |
| Process |
Processing |
Completion messages — past/完了 form
| Wrong |
Correct |
| Save |
Saved / Save complete |
| Translate |
Translation complete |
Empty state — negative existence
| Wrong |
Correct |
| Results are empty |
No results / No results found |
| Not selected |
Not selected |
Drag and drop
| English |
Japanese |
| drag |
Drag |
| drop |
Drop |
| release (let go) |
Release — NOT Release |
| browse (file picker) |
Select / Choose file — NOT 参照 |
Validation messages
Use connectors: and/and (and), or (or), only (only). Always polite form.
- Wrong:
3-50文字、文字、数字、ハイフンのみ
- Correct:
3-50文字。使用可能：英字、数字、ハイフン
- Wrong:
パスワードが短すぎる → Correct: パスワードが短すぎます
Other UI patterns
| Wrong |
Correct |
Reason |
| Alternative detection |
Alternative detection method |
Labels need complete noun phrases |
| Automatic |
Automatic mode |
Bare adjectives need completing nouns |
| 25+ languages |
25 or more languages |
"N+" → N or more 〜 |
| +N more items |
{count} more / {count} remaining |
"+N more" pattern |
Keigo Consistency
Maintain ONE level throughout. Mixing is the most common error.
| Don't mix |
Use |
| Please change + click |
Please change + please click |
| Please confirm + saved |
Please confirm + saved |
UI labels (buttons) stay in stem form regardless of keigo level used in sentences.
Punctuation — full-width in Japanese text
Use 。、：「」！？（）. Half-width for URLs, emails, code, English text.
| Wrong |
Correct |
| Status: Complete |
Status**:**Complete |
| Please confirm,save |
Please confirm**,**save |
| Email: user@example.com |
Email**:**user@example.com (full-width colon, but email stays half-width) |
Spacing (Spacing)
- Space between Japanese and Latin script/numbers:
API 設定 not API設定, 合計 10 件 not 合計10件.
- No space between Japanese characters:
保存する not 保存 する.
Native vs Loanword — prefer native for UI
| Avoid (katakana) |
Use (native) |
| Save |
Save |
| Setting |
Settings |
| Select |
Select |
| Target Audience |
Target user |
| Casual (for speech tone) |
Casual / informal |
カジュアル describes fashion. For communication register, use くだけた or 気軽な. UI tone vocabulary: フォーマル、くだけた、プロフェッショナル.
Keep katakana ONLY for: established loanwords (Upload, Download, Cancel, Login), foreign brand names, technical abbreviations (API, URL, ID).
Honorific Prefixes お (o-) / ご (go-)
Honorific prefixes attach to nouns to elevate the referent. Used in formal register; minimized in informal.
Rule of thumb
- お attaches to native Japanese words (和語 / wago): お名前 (name), お時間 (time), お電話 (phone call), お知らせ (notice), お支払い (payment), お申し込み (application), お問い合わせ (inquiry)
- ご attaches to Sino-Japanese words (漢語 / kango): ご連絡, ご利用, ご確認, ご質問, ご注文, ご登録, ご案内
- Test: native word → お ; Chinese-origin word → ご
- Exceptions exist (e.g., ご飯 is wago but takes ご; お電話 looks kango but takes お). Memorize the common UI ones below.
Register usage
- Formal register: apply liberally to customer-facing nouns
- Informal register: drop from non-essential nouns (
登録 instead of ご登録 is fine in casual UI)
- 謙譲語 (humble) contexts referring to ONE'S OWN action: do NOT attach お/ご to your own action. e.g., when YOU are applying, write
申し込む, NOT お申し込みする. Reserve お申し込み for referring to the customer's action.
Common UI examples
| Japanese |
English |
| お名前 |
name (customer's) |
| お時間 |
time (customer's) |
| お支払い方法 |
payment method |
| お知らせ |
notification |
| お問い合わせ |
inquiry / contact |
| ご利用規約 |
terms of use |
| ご登録 |
registration |
| ご確認 |
confirmation |
| ご連絡 |
contact / communication |
| ご注文 |
order |
| ご案内 |
guidance / information |
| ご質問 |
question |
False Friends (和製英語)
| Katakana |
Means in Japanese |
Correct for English meaning |
| Apartment |
apartment/condo |
Mansion (for "mansion") |
| Buffet |
buffet |
(Viking warrior - rarely needed) |
| Smart |
slim/slender |
Intelligent (for "intelligent") |
| Tension |
excitement/high energy |
Tension (for "stress/tension") |
Calques to avoid
| Literal (wrong) |
Natural Japanese |
| Make sense |
Makes sense |
| At the end of the day |
In the end |
| On the table (abstract) |
On the agenda |
| The ball is in your court |
It's up to you |
| Break a leg |
Good luck! / Best wishes |
| Piece of cake |
Piece of cake / Easy |
| When pigs fly |
No way / Impossible |
Compound Adjectives
| English pattern |
Wrong |
Correct |
| X-aware |
Context-aware |
Context-aware |
| AI-powered/driven |
AI-driven |
AI-powered / AI-equipped |
Compound Descriptive Nouns
Decompose English compounds, rebuild with Japanese noun-modification syntax.
- "mom creators" →
ママクリエイター or 子育て中のクリエイター (NOT 母親作成者)
- "niche creators" →
ニッチ分野のクリエイター or 専門クリエイター
- "English-speaking customer service" →
英語対応の顧客サービス (compound adjective, NOT participial)
Spatial Metaphor Prepositions (adapt, don't translate literally)
| English (figurative) |
Use |
Don't use |
| under [category] |
Among / In |
Under |
| on top of (in addition) |
In addition to |
On top of |
| behind the scenes |
Behind the scenes / Backstage |
(literal) |
| within [timeframe] |
Within |
Inside |
UI Element Reference in Prose
When referencing a UI label by name in running prose, bracket it:
- Wrong:
名前のフィールド → Correct: 「名前」フィールド or ［名前］フィールド
- Wrong:
アカウントのタブ → Correct: 「アカウント」タブ
- Generic elements (
検索バー) need no brackets.
Temporal Simile Restructuring
English similes like "like it's [YEAR]" / "stuck in [YEAR]" imply "outdated / frozen in time". Literal [YEAR]年のまま + 動詞 sounds unnatural.
| English |
Wrong |
Natural |
| operating like it's 1995 |
Still running on 1995 |
Nothing has changed since 1995 / It's as if time stopped in 1995 |
| stuck in [YEAR] |
Stuck in [YEAR] |
Hasn't progressed since [YEAR] / Still in the [YEAR]s |
Polysemy — pick the right sense for the domain
| Word |
Wrong (literal) |
Correct (contextual) |
| copy (marketing) |
Copy/Duplicate |
Copy (text) / Wording |
| sauce (figurative) |
Source |
Secret / Key |
| bug (software) |
Bug |
Bug |
| resume (verb) |
Resume |
Resume |
Proper Nouns — natural form in UI
| Formal/news |
UI/casual |
| USA |
America |
| UK |
United Kingdom |
| United States of America |
America |
Name Suffixes (Honorifics)
Suffixes attach to a person's name to convey respect level. Choosing the wrong one is a noticeable formality error.
| Suffix |
Formality |
When to use in UI |
| Sama (sama) |
Highest — customer-facing |
Addressing the customer in messages: 田中様、ようこそ。 |
| san (san) |
Neutral polite |
Internal references, casual customer touch, community apps |
| Dono (dono) |
Outdated / archaic |
Avoid in modern UI; appears only on formal certificates |
| Sensei (sensei) |
Profession-respect |
Teachers, doctors, lawyers, authors |
| Chan / Kun (kun) |
Diminutive / casual |
Avoid in UI unless target audience is kids/casual community |
Rules
- Do NOT attach a suffix to one's own name. The brand/sender never self-applies 様/さん.
- Personalized greetings address the recipient only:
田中様、ようこそ。 — NOT 田中様、私田中ようこそ。
- When in doubt for customer-facing UI: use 様.
- For internal dashboards / team-facing UI: さん is more natural than 様.
Question / Confirmation Phrasing
- Wrong:
あなたは確かですか？ → Correct: よろしいですか？
- Wrong:
これを本当に削除しますか？ → Correct: この項目を削除してもよろしいですか？
- End yes/no questions with
か in polite form. Omit pronouns.
Cultural Conventions
| Item |
Format |
| Date |
2024年1月15日 (NOT 01/15/2024) |
| Time |
14時30分 or 14:30 |
| Currency |
¥1,000 or 1,000円 |
Number Formatting
Numerals
- Thousands separator: comma —
1,000, 10,000, 1,234,567
- Decimal point: period —
3.14, 0.5
- Large units use kanji groupings (not Western thousands/millions/billions):
| Numeral |
Japanese |
Meaning |
| 10,000 |
1万 |
ten thousand |
| 100,000 |
10万 |
hundred thousand |
| 1,000,000 |
100万 |
one million |
| 10,000,000 |
1,000万 or 1千万 |
ten million |
| 100,000,000 |
1億 |
hundred million |
| 1,000,000,000,000 |
1兆 |
trillion |
Currency
¥1,000 (symbol-first, Western style)1,000円 (number + 円, more native)- Large amounts:
1万円, 100万円, 1億円
Date
| Format |
Use case |
2024年1月15日 |
Standard / full — preferred in UI body copy |
2024/01/15 |
Slash form — tables, logs, compact UI |
2024-01-15 |
ISO — technical / API contexts |
R6/01/15 or 令和6年1月15日 |
Reiwa era — formal/government/legal only |
Time
| Format |
Use case |
14:30 |
24-hour, compact — preferred in UI |
14時30分 |
24-hour, native — body copy / formal |
午後2時30分 |
12-hour with 午前/午後 — casual / spoken style |
Counters (助数詞) — expansion
| Counter |
Use for |
| 人 (nin) |
People (general) |
| 名 (mei) |
People (formal, business — 5名様) |
| 件 (ken) |
Cases, records, inquiries, results |
| 個 (ko) |
General small objects |
| 枚 (mai) |
Flat things — paper, photos, tickets, cards |
| 冊 (satsu) |
Bound items — books, magazines, notebooks |
| 台 (dai) |
Machines, vehicles, devices |
| 本 (hon) |
Long thin objects — bottles, pencils, calls |
| 杯 (hai) |
Cups, glasses, bowls of liquid |
| 匹 (hiki) |
Small animals — cats, dogs, fish |
| 頭 (tou) |
Large animals — cattle, horses |
| 階 (kai) |
Floors of a building |
| 番 (ban) |
Number / turn / ranking |
| 語 / Language |
Languages |
Greeting and Closing Conventions
Spoken / time-of-day greetings
| Japanese |
Use |
| Good morning |
Morning |
| Hello |
Daytime |
| Good evening |
Evening |
| お疲れ様です |
Workplace standard — "thank you for your hard work" |
| Nice to meet you |
First meeting introduction |
UI welcome
ようこそ — formal welcome (ようこそ、田中様。)こんにちは — neutral / informal welcome
Email openings
| Japanese |
Formality |
| お世話になっております |
Standard business |
| 平素より大変お世話になっております |
More formal / first-touch enterprise |
| Thank you as always |
Warm / customer-facing |
Email closings
| Japanese |
Formality |
| よろしくお願いいたします |
Standard |
| 何卒よろしくお願い申し上げます |
Very formal |
| 引き続きよろしくお願いいたします |
Ongoing relationships |
Cost / Estimate Expression Ordering
Be explicit about whether the amount is per-item or total.
- Pattern A (amount-first):
{credits}クレジット（{count}言語分）
- Pattern B (scope + 合計):
{count}言語で合計{credits}クレジット
- Ambiguous (wrong):
{count}言語{credits}クレジット — could mean per-language OR total.
Redundant Modifiers — remove
| Wrong |
Correct |
| {min} characters long |
{min} characters or more |
| Round-shaped |
Round |
| Save your file |
Save file (omit pronoun) |
Self-Check Checklist (run before finalizing)
Accuracy
- Particles correct (を/に/で/の/から)
- Measure words appropriate (言語/件/個/人/枚)
- Word vs character not confused (単語 vs 文字)
- FOR vs PER not confused (〜で/分 vs 〜あたり/につき)
- Unit words added after numeric placeholders (秒/分/時間/日)
- Temporal: 〜後 for countdowns, 〜中 for ongoing, 〜以内に for deadlines
- Placeholder type markers added (形式の, 言語の)
- Keigo level consistent throughout
- UI buttons in stem form; sentences in です/ます
- Full-width punctuation (。、：「」)
- SOV word order
- Script choice correct (hiragana=grammar, katakana=foreign, kanji=meaning)
- Spacing: gap between Japanese ⇄ Latin/numbers; none between Japanese characters
- All
{variables} and ICU intact
- Domain terminology uses IT loanwords (Architecture, Deploy, Pipeline)
Naturalness
- UI labels are complete noun phrases (代替検出方法, NOT 代替検出)
- Cost expressions use amount-first or scope+合計 pattern
- Tone vocabulary correct (casual, NOT casual for speech)
- No English idioms translated literally (calques)
- Pronouns omitted when context clear
- Compound adjectives natural (AIを活用した, NOT AI駆動型)
- Drag-drop verbs correct (離す for release, NOT リリース)
- Native term over loanword when both exist (保存 > セーブ)
- Compound nouns restructured (ママクリエイター, NOT 母親作成者)
- UI labels in prose use 「」brackets
- Spatial metaphors adapted (〜の中から, NOT 〜の下に)
- False friends not used in wrong sense (Apartment ≠ mansion)
- Validation messages polite + clear structure
Worked Example
Source: "Welcome! Please select your file to upload — we support 25+ formats and translate it for 5 languages in {seconds}s. Don't worry, you can cancel at any time."
Wrong (literal):
Welcome! Please browse your files to upload — we support 25+ formats and will translate it into 5 languages in {seconds}. Don't worry, you can cancel anytime.
Issues: あなたへ (unnatural), あなたの (redundant), 参照 (wrong UI verb), 25+ (not natural quantity), 5言語につき (FOR/PER confusion, says PER), {seconds} (missing unit), 心配しないで (calque).
Correct:
Welcome! Please select the file to upload. It supports 25+ formats and will translate into 5 languages within {seconds} seconds. You can cancel anytime.
