十分 (juubun) conjugation
enough
十分 (じゅうぶん, juubun) 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 | 十分だ juubunda | 十分です juubundesu | The form you look up. Also the casual “is ~”. |
| Negative | 十分じゃない juubunjanai | 十分じゃないです juubunjanaidesu | “is not ~”. |
| Past | 十分だった juubundatta | 十分でした juubundeshita | “was ~”. |
| Past negative | 十分じゃなかった juubunjanakatta | 十分じゃなかったです juubunjanakattadesu | “was not ~”. |
| Te-form | 十分で juubunde | — | Links to the next clause: “~ and …”. |
| Adverb | 十分に juubunni | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 十分な〜 juubunna〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 十分なら juubunnara | — | “if it is ~”. |
| Conditional (~たら) | 十分だったら juubundattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 十分になる juubunninaru | 十分になります juubunninarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 十分すぎる juubunsugiru | 十分すぎます juubunsugimasu | “too ~”. |
| Looks ~ (~そう) | 十分そう juubunsou | 十分そうです juubunsoudesu | “looks / seems ~” from appearance. |
🔊 Tap any Japanese word to hear it spoken.
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.