How to say "confidential" in Japanese

• 内々うちうちCommon
  no-adjective, adverbCovers things kept private or confidential among a small circle, often informal. Used for matters handled quietly within a company or family rather than for stamped documents, e.g. a discussion settled 内々.
  このことは内々ないないにしてください。↗

  Please keep this a secret.
• マル秘まるひ
  no-adjectiveRefers to documents or information marked secret or classified, evoking the ㊙ symbol. Choose this when 'confidential' describes officially designated files rather than simply private matters.
  報道ほうどう機関きかんは現職げんしょく議員ぎいんについてはいつもマル秘まるひ情報じょうほうをつかんでいます。↗

  The press always has something on the incumbent.
• 親展しんてん
  no-adjectiveUsed for mail or correspondence, meaning it must be opened by the addressee personally; 'confidential' on an envelope. This is its main use, so it is not a general adjective for confidential information.
• コンフィデンシャル
  no-adjectiveThe loanword, used in business and legal contexts, often as a label such as on documents or in company names. If you simply want an adjective meaning 'confidential', this loanword is frequently the most direct choice.
• 内分ないぶん
  noun, suru verbMeans 'in secret' or 'privately', and matches 'confidential' only loosely; it is a less common word and seldom the one you want. Prefer 内々 or another entry for ordinary confidential matters.

内々 covers private, informal matters kept among insiders; 「マル秘」 and 親展 suit documents marked confidential; 「コンフィデンシャル」 is the loanword; 内分 is a rare way to say 'in secret'.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 内々うちうちprivate
• マル秘まるひconfidential
• 親展しんてんconfidential
• コンフィデンシャルconfidential
• 内分ないぶんsecret
• 部外秘ぶがいひrestricted
• 直披じきひpersonal