後悔|こうかいkoukai[1]atamadaka (head-high)

1. suru verb, transitive verb, intransitive verb, no-adjectiveregret; repentance; remorse
   今更いまさら後悔こうかいしても無駄むだだ。↗

   It's no use regretting it now.

• Synonym悔いくいWrittenWritten style. A noun for the feeling of regret, mostly in set phrases like 「悔いが残る」.
• Synonym悔いるくいるWrittenWritten style. A verb for realizing your own conduct was wrong and regretting it, stressing reflection: 「罪を悔いる」.
• Synonym思い残すおもいのこすWrittenWritten style for having lingering regrets, typically in the negative: 「思い残すことはない」.
• Synonym悔恨かいこんFormalFormal term for deep, painful remorse, as in 「悔恨の念」; stronger than 後悔.
• Related悔やむくやむNeutralA verb covering both regretting a failure (「失敗を悔やむ」) and mourning a death (「お悔やみ」); broader in range than 後悔.
• RelatedうらむFormalFormal written style for feeling regret, mostly in set phrases such as 「〜の憾みがある」.
• Related悔しがるくやしがるCasualColloquial. For outwardly showing bitterness or frustration, as in 「負けて悔しがる」; describes visible behavior, not the feeling itself.
• Related無念がるむねんがるWrittenWritten style and rare. For feeling deep regret over something that didn't turn out as hoped.
• Related自責の念じせきのねんWrittenWritten set phrase for guilt and self-reproach over one's own actions, as in 「自責の念に駆られる」.
• Related残念に思うざんねんにおもうNeutralSet expression for feeling regret; somewhat solemn in tone.
• Related残念がるざんねんがるCasualColloquial. For visibly showing disappointment, as in 「残念がる顔」; about the outward show, not inner regret.
• Antonym満足まんぞくNeutralAntonym: being fully content, with no complaints or regrets — the opposite of 後悔.

Use 「後悔」 for regretting, after the fact, what you did or didn't do (「後悔先に立たず」, 「後悔している」). For the feeling of regret say 「悔い」, for deep remorse 「悔恨」, for self-reproach 「自責の念」. The opposite is 「満足」.

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

1. 後あとになって自分じぶんのしたことやしなかったことを悔くやむこと。