悔しい (kuyashii) conjugation
regrettable, mortifying, vexing
悔しい (くやしい, kuyashii) is an i-adjective. I-adjectives carry their own tense: drop the final い and the endings attach straight to the stem. No だ, no です needed to make a complete sentence.
Conjugation table
| Form | Plain (casual) | Polite (~です) | When you use it |
|---|---|---|---|
| Dictionary / plain | 悔しい kuyashii | 悔しいです kuyashiidesu | The form you look up. Also the casual “is ~”. |
| Negative | 悔しくない kuyashikunai | 悔しくないです kuyashikunaidesu | “is not ~”. |
| Past | 悔しかった kuyashikatta | 悔しかったです kuyashikattadesu | “was ~”. |
| Past negative | 悔しくなかった kuyashikunakatta | 悔しくなかったです kuyashikunakattadesu | “was not ~”. |
| Te-form | 悔しくて kuyashikute | — | Links to the next clause: “~ and …”. |
| Adverb | 悔しく kuyashiku | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 悔しい〜 kuyashii〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 悔しければ kuyashikereba | — | “if it is ~”. |
| Conditional (~たら) | 悔しかったら kuyashikattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 悔しくなる kuyashikunaru | 悔しくなります kuyashikunarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 悔しすぎる kuyashisugiru | 悔しすぎます kuyashisugimasu | “too ~”. |
| Looks ~ (~そう) | 悔しそう kuyashisou | 悔しそうです kuyashisoudesu | “looks / seems ~” from appearance. |
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Why it conjugates this way
I-adjectives carry their own tense: drop the final い and the endings attach straight to the stem. No だ, no です needed to make a complete sentence.
See the full rules in the adjective conjugation guide.