利口 (rikou) conjugation
clever, shrewd, bright
利口 (りこう, rikou) is a na-adjective. Na-adjectives behave like nouns. The word itself never changes — you conjugate だ/です after it, and you need な to put it in front of a noun.
Conjugation table
| Form | Plain (casual) | Polite (~です) | When you use it |
|---|---|---|---|
| Dictionary / plain | 利口だ rikouda | 利口です rikoudesu | The form you look up. Also the casual “is ~”. |
| Negative | 利口じゃない rikoujanai | 利口じゃないです rikoujanaidesu | “is not ~”. |
| Past | 利口だった rikoudatta | 利口でした rikoudeshita | “was ~”. |
| Past negative | 利口じゃなかった rikoujanakatta | 利口じゃなかったです rikoujanakattadesu | “was not ~”. |
| Te-form | 利口で rikoude | — | Links to the next clause: “~ and …”. |
| Adverb | 利口に rikouni | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 利口な〜 rikouna〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 利口なら rikounara | — | “if it is ~”. |
| Conditional (~たら) | 利口だったら rikoudattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 利口になる rikouninaru | 利口になります rikouninarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 利口すぎる rikousugiru | 利口すぎます rikousugimasu | “too ~”. |
| Looks ~ (~そう) | 利口そう rikousou | 利口そうです rikousoudesu | “looks / seems ~” from appearance. |
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Why it conjugates this way
Na-adjectives behave like nouns. The word itself never changes — you conjugate だ/です after it, and you need な to put it in front of a noun.
See the full rules in the adjective conjugation guide.