Guidance for Japanese

Proton Localization Style Guide for Japanese.

Last Update: January 27, 2025.

If you have any comments, suggestions, questions or need for an arbitration, create a topic in the Japanese Language Community section, the Language Lead will get back to you.

Here you will find the guidance for Japanese, but you should also consider the guidance for all languages.

1. Capitalization - 大文字の使用

  • Please do Capitalize Proper names and leave as they are. such as follow:
    • Proton Mail(No プロトンメール)
    • Proton VPN(No プロトンVPN)
    • Proton Drive(No Protonドライブ)
    • NetShield(No ネットシールド)

2. Abbreviations - 省略形

Whenever possible, avoid using abbreviations.

Abbreviate the text only when you lack space (mainly buttons, option names or strings with specific character limitations) or when you need to ease the text readability. In particular, it can be very difficult to determine whether “月” and “日” refer to Monday and Sunday, or to the month and day. You must pay attention to the context.

English Translation Abbreviation
Monday 月曜日
Tuesday 火曜日
Wednesday 水曜日
Thursday 木曜日
Friday 金曜日
Saturday 土曜日
Sunday 日曜日

3. Acronyms - 頭字語

  • Common examples are VPN (Virtual Personal Network), DNS (Domain Name Server), HTML (Hypertext Markup Language), etc.
  • The most common acronyms and their translations are included in the glossary. Always refer to the glossary when localizing acronyms.
  • Commonly used acronyms do not need explanations (DVD, LED, TV, etc.).
  • When an acronym is repeated several times in the same section, include its extended form in parentheses only for its first occurrence.

4. Pronouns - 代名詞

  • English, especially technical English, is more redundant than some other languages.
  • When translating, you often need to reduce the redundancy of the source text using pronouns. This may otherwise affect the text readability. However, this must not affect accuracy.
  • When translating technical and complex strings, ensure users can associate pronouns to the noun they refer to.
  • Avoid the use of possessive pronouns when possible.
  • Omit pronoun subjects such as “we” and “you".

5. Gerunds - 動名詞

  • Gerunds are used in English, such as in “Creating a report”.
  • When paragraph and chapter heads begin in English with a gerund, as a general rule please use an infinitive, translating it as the equivalent of “Create a report”.
  • Depending on the context, this may also mean “in the process of”.
English We avoid We prefer
Protecting your digital identity デジタルアイデンティティを保護しています デジタルアイデンティを保護する
Generating keys キー生成 キー生成中

6. Punctuation - 句読点

  • Basically it translates “.” to “。” and “,” to “、”.
  • However, there are exceptions where it can be used when you need to ease the text readability.
  • The translations are not too long, but sometimes they are long, so please use punctuation when reading long sentences.

6.1 Period - 終止符

  • For the period at the end of a sentence (subject + verb), adapt the source to your language usage: when the English source does not put a period at the end of the sentence (subject + verb), but should in your language, add it in your translation. In this case, make sure that the text you are translating is not a part of a longer sentence (this is usually specified in the context).
  • Include a period at the end of each extended sentence in a bullet list if this sentence has a full meaning by itself.
  • Unless the item includes more than one sentence, do not place any periods at the end of titles, links, buttons and checkboxes.

6.2 Exclamation mark - 感嘆符

  • Exclamation marks are used to give emphasis.
  • Basically it translates “!” to “!”.

6.3 Parentheses - 挿入語句

  • Parentheses are used to clarify statements or provide additional information.
  • Let’s avoid parentheses as much as possible and adapt to the context.
English We avoid We prefer
two-factor authentication(2FA) 二要素認証(2FA) 二要素認証
We also support importing vCard.(UTF-8 encoding) vCardもインポートできます。(UTF-8エンコーディング) (UTF-8エンコードされた)vCardもインポートできます。

6.4 Comma - コンマ

  • When a sentence contains three or more words, just leave “,” as is. The final “and” does not need to be written as “そして”.
  • Do not place a comma before “or” when the conjunction is used to link two related terms.
English We avoid We prefer
You can also add, delete, and edit them by clicking… クリックして追加、削除、そして編集できます… クリックして追加、削除、編集できます…
Assign permissions to users, or groups ユーザー、またはグループに権限を付与する ユーザーまたはグループに権限を付与する

6.5 Colon and semicolon - コロンとセミコロン

  • Colons and semicolons are all preceded by a non-breaking space.

6.6 Em dash, en dash, hypen - ダッシュとハイフン

  • In English, an Em or En dash is used to demarcate an isolated element, to introduce an item that is not essential to the sentence’s meaning, to emphasize a sudden change in thought or to bring focus to a list.
  • It is often more appropriate to use a comma, a full stop or parenthesis instead.
  • Do not use Em dash.

6.7 Quotation marks - 引用符

  • Use " quotation marks.

6.8 Apostrophes - アポストロフィー

  • Do not use apostrophes.

7. Spacing and non-breaking spaces - スペース

  • Use non-breaking spaces to prevent improper division of elements such as product names, part numbers, numbers, dates, etc.
  • When using currency symbols or units of measurement, include a non-breaking space between number and sign.
  • To insert a non-breaking space using your keyboard:
    • On Windows, hold down the “Alt” key while typing the number “255”.
    • On Apple, Ctrl + Option⌥ + Space bar.

8. Numbers - 数字

  • For numbers smaller than 1, always put a zero before the decimal comma.
    • .5 => 0.5
  • The period in app/software version numbers remains unchanged.
    • Proton Mail v.3
  • As a thousand separator, use a comma. Never use thousand separators in years.
    • 15000 => 15,000
    • 2,024 => 2024
  • Time and date:
    • Hours and minutes are separated by a colon. Use the 12 hour format to specify A.M. and P.M.
      • at 10:30 P.M => 午後10:30
    • The date format is “yyyy-MM-dd”.
      • 01-31-24(MM/dd/yy) => 2024-01-31
      • 20th Jan 2024 => 2024年1月20日

9. Ordinal numbers - 序数

  • Ordinal numbers may be written in with numerals and letter suffixes, where the suffix acts as an ordinal indicator.

10. Currencies - 通貨

  • Do not convert USD($) or EUR(€) amounts to local currency YEN(¥).
  • Place the symbol $, € before the number and separate it with a non-breaking space from the number.

11. Units of measurement - 寸法単位

  • Use the metric system.
  • Use unit symbol as abbreviation.
  • Insert a non-breaking space between a number and the relevant unit.
  • Using unit symbol over translation is recommended.
  • Convert imperial units into metric units.
    • 6 feet => 183 cm
Measurement unit Translation Abbreviation
Kilometer キロメートル km
Meter メートル m
Centimeter センチメートル cm
Millimeter ミリメートル mm
Ton トン t
Kilogram キログラム kg
Pound ポンド lb
Inch インチ in
Feet フィート ft
Mile マイル mi
Gallon ガロン gal
Byte バイト B
Megabyte メガバイト MB
Gigabyte ギガバイト GB
Terabyte テラバイト TB

12. English / US terms - 用語

  • Please => お願い
  • Now => 現在
  • Successfully => 成功
  • Failed => 失敗
  • NOTE: => 注意:
  • notes => メモ
  • items => アイテム

13. Foreign words - 外来語

  • The decision about the use of foreign words (keeping it in English) rather than an equivalent term in your language is based on how widespread the use of the word is. An English term might be recommended when its use has become very common.
  • To find out how common a word is, you can use internet search engines. Search for the English word and for the corresponding translation in your language on your preferred search engine. The number of occurrences in each case will be an indication of how popular the use of each word is. If in doubt for an important term, ask Proton Localization team to make an SEO (Search Engine Optimization) check.
  • Foreign words might be accompanied by quotation marks or italics when their use is not widely spread. However, English words that are widely accepted for use are kept as they are in the original but do not take the ending “s” in the plural case.
  • When foreign words are common and well understood, they can be left in the source language. Where necessary, add an explanation in the target language.
  • Avoid using too many anglicisms.

14. Localizing person names - 人物名

  • Localize fictitious person names used for explanatory purposes, choosing a name that is generic but not stereotypical.
    • Please enter your display name (e.g. Julia Smith) => 表示名を入力してください(例:田中 太郎)
  • Do not localize real persons’ names.
    • Bart Butler is a senior engineer at Proton Mail. => Bart ButlerはProton Mailのシニアエンジニアです。

15. Localizing domains and email adresses - ドメイン名とメールアドレス

Do not need localize fictitious domain names and mail addresses used for explanatory purposes:

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