How to say "sincerely" in Japanese

• くれぐれもJLPT N2approx.Common
  adverbCovers 'sincerely' as 'earnestly, with utmost care': it fits earnest requests, warnings, apologies, and parting words of concern, and it is not a way to close a letter.
  くれぐれもお体からだをお大事だいじに。↗

  Please take good care of yourself.
• 心からこころからCommon
  adverbThe natural choice when 'sincerely' means 'from the bottom of your heart': heartfelt thanks, apologies, sympathy, or congratulations. It presents the feeling as genuine and deeply meant.
  彼かれは心こころから彼女かのじょを迎むかえた。↗

  He greeted her with cordiality.
• ではまたCommon
  expressionSeldom the word you want for 'sincerely': it is really a casual 'see you later' or goodbye, matching 'sincerely' only as a friendly sign-off to a message.
  ではまた明日あす。↗

  See you again tomorrow.
• 誠にまことにJLPT N1approx.Common
  adverbReaches 'sincerely' only through its sense of 'truly': a polite adverb that strengthens formal apologies, thanks, and announcements, where it reads as 'truly' or 'very' rather than as heartfelt.
  遅おくれまして、誠まことに申し訳もうしわけありません。↗

  I'm awfully sorry that I was late.
• 心底しんそこCommon
  adverbIts 'sincerely' is emphatic: the feeling is genuine all the way down. It suits strong statements of deep emotion rather than polite expressions of thanks or apology.
  君きみには心底しんそこ失望しつぼうしたよ。↗

  I'm very disappointed in you.

Use 「心から」 for heartfelt sincerity in thanks or apologies, 「誠に」 for formal 'truly', 「くれぐれも」 for earnest urging or well-wishing, 心底 for deeply felt emotion, and 「ではまた」 only as a casual farewell, never for sincerity.

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

• くれぐれもsincerely
• 心からこころからfrom the bottom of one's heart
• ではまたsee you later
• 誠にまことにreally
• 素ですでgenuinely
• 深くふかくdeeply
• 真心を込めてまごころをこめてwholeheartedly
• 心底しんそこfrom the bottom of one's heart
• ひとえにearnestly
• 重ね重ねかさねがさねexceedingly