内緒・内証・内所|ないしょnaisho[0]heiban (flat)

1. no-adjectivesecrecy; confidentiality; privacy; secret
   彼女かのじょは内緒ないしょで私にその話はなしをした。↗

   She told me the story in confidence.
2. no-adjectiveone's circumstances (esp. fiscal)
3. no-adjective, Buddhisminner realization; personal enlightenment
4. no-adjectivekitchen

• Synonym秘密ひみつNeutralNeutral, broad-range word for a secret, as in 「秘密を守る」; 「内緒」 is more colloquial and centres on private matters kept from others.
• Synonym内々うちうちNeutralPrivate handling among one's own — family, workplace or organization — as in 「内々に済ます」; 「内緒」 stresses hiding things from others.
• Synonym内密ないみつWrittenWritten/formal word for confidential matters, stressing that they not be passed on, as in 「内密にお願いします」.
• Synonym非公開ひこうかいWrittenFormal, written term for keeping information or meetings closed to outsiders, as in 「非公開会議」.
• Synonym秘め事ひめごとWrittenWritten word for hidden private matters with a secretive feel; often a romantic affair between a man and a woman.
• RelatedプライバシーNeutralLoanword for privacy; stresses one's personal life being free from outside interference.
• Related隠し立てかくしだてNeutralDeliberate concealment; stresses the attitude of keeping something hidden and not telling.
• Antonym表向きおもてむきNeutralThe public, official side of things; the opposite of 「内緒」, which is done behind closed doors.
• Antonym公おおやけNeutralMeans 'you' or, as 「公」, 'ruler'; has no opposition to 「内緒」 and was likely included in error.

Colloquial 「内緒」 is the everyday choice for keeping something from others, as in 「みんなには内緒ね」 or 「内緒話」. Use 「秘密」 for secrets in general, 「内密」 in writing, and 「内々」 for matters handled privately among insiders. 「隠し立て」 stresses deliberate withholding, 「プライバシー」 personal privacy, 「非公開」 formal non-public status; 「表向き」 is the public opposite.

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

1. 公表こうひょうせず、内々ないないにすること。内密ないみつにすること。
2. 表向おもてむきでない、奥おくの間あいだ、台所だいどころ。また、経済けいざい状態じょうたい。