良い (yoi) conjugation
good, nice
良い (よい, yoi) 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.
よい is usually said いい. いい is the everyday dictionary form, but it borrows よ- for everything else: よくない, よかった, よくて. いくない and いかった do not exist.
Conjugation table
| Form | Plain (casual) | Polite (~です) | When you use it |
|---|---|---|---|
| Dictionary / plain | 良い yoi | 良いです yoidesu | The form you look up. Also the casual “is ~”. |
| Negative | 良くない yokunai | 良くないです yokunaidesu | “is not ~”. |
| Past | 良かった yokatta | 良かったです yokattadesu | “was ~”. |
| Past negative | 良くなかった yokunakatta | 良くなかったです yokunakattadesu | “was not ~”. |
| Te-form | 良くて yokute | — | Links to the next clause: “~ and …”. |
| Adverb | 良く yoku | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 良い〜 yoi〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 良ければ yokereba | — | “if it is ~”. |
| Conditional (~たら) | 良かったら yokattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 良くなる yokunaru | 良くなります yokunarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 良すぎる yosugiru | 良すぎます yosugimasu | “too ~”. |
| Looks ~ (~そう) | 良さそう yosasou | 良さそうです yosasoudesu | “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.