速い (hayai) conjugation
fast, quick
速い (はやい, hayai) 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 | 速い hayai | 速いです hayaidesu | The form you look up. Also the casual “is ~”. |
| Negative | 速くない hayakunai | 速くないです hayakunaidesu | “is not ~”. |
| Past | 速かった hayakatta | 速かったです hayakattadesu | “was ~”. |
| Past negative | 速くなかった hayakunakatta | 速くなかったです hayakunakattadesu | “was not ~”. |
| Te-form | 速くて hayakute | — | Links to the next clause: “~ and …”. |
| Adverb | 速く hayaku | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 速い〜 hayai〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 速ければ hayakereba | — | “if it is ~”. |
| Conditional (~たら) | 速かったら hayakattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 速くなる hayakunaru | 速くなります hayakunarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 速すぎる hayasugiru | 速すぎます hayasugimasu | “too ~”. |
| Looks ~ (~そう) | 速そう hayasou | 速そうです hayasoudesu | “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.