内々・内内|うちうちuchiuchi[0]heiban (flat)

1. no-adjective, adverbprivate; confidential; informal; secret; (within the) family circle; (on the) inside
   このことは内々ないないにしてください。↗

   Please keep this a secret.

• Synonym内密ないみつNeutralEmphasizes secrecy more than 「内々」— keeping outsiders from knowing, as in 「内密に処理する」.
• Synonym内緒ないしょCasualColloquial word for hiding something from others, as in 「内緒の話」; carries a friendly, private tone.
• Synonym秘密ひみつNeutralThe broadest word: a hidden thing, a secret, also a mystery; 「内々」 specifically stresses keeping things among insiders.
• Synonym非公開ひこうかいNeutralMeans closed to the general public, as in 「非公開の会議」; focuses on whether something is made public, and leans formal.
• Related密々みつみつWrittenWritten adverb meaning secretly, quietly; rare, and everyday speech prefers 「内々に」 or 「こっそり」.
• Related内密にないみつにNeutralAdverb form: privately, not openly; used to ask someone to keep things confidential, as in 「内密にお願いします」.
• Antonym表向きおもてむきNeutralOn the surface; officially or publicly stated — the direct opposite of the private, insider sense of 「内々」.
• Antonym公おおやけNeutralAs 「きみ」 this is a second-person pronoun for peers or juniors, with no antonym link to 「内々」; the word meaning 'public' is 「公（おおやけ）」.

Use 「内々」 for matters handled privately among insiders, as in 「内々に打診する」. To stress secrecy say 「内密」; in casual speech say 「内緒」; the opposite is 「表向き」.

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

1. 内輪うちわの者ものだけで物事ものごとを行おこなうこと。
2. 心こころの内うち。
3. （ないない、うちうち）密ひそかに。こっそり。
4. （ないない）心こころの内うちで密ひそかに思おもったり感かんじたりするさま。