丈夫 (joubu) conjugation
strong, solid, durable
丈夫 (じょうぶ, joubu) 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 | 丈夫だ joubuda | 丈夫です joubudesu | The form you look up. Also the casual “is ~”. |
| Negative | 丈夫じゃない joubujanai | 丈夫じゃないです joubujanaidesu | “is not ~”. |
| Past | 丈夫だった joubudatta | 丈夫でした joubudeshita | “was ~”. |
| Past negative | 丈夫じゃなかった joubujanakatta | 丈夫じゃなかったです joubujanakattadesu | “was not ~”. |
| Te-form | 丈夫で joubude | — | Links to the next clause: “~ and …”. |
| Adverb | 丈夫に joubuni | — | Turns it into “~ly”, describing a verb. |
| Before a noun | 丈夫な〜 joubuna〜 | — | How it attaches when it modifies a noun. |
| Conditional (~ば/なら) | 丈夫なら joubunara | — | “if it is ~”. |
| Conditional (~たら) | 丈夫だったら joubudattara | — | “if / when it is ~”. The everyday conditional. |
| Become (~なる) | 丈夫になる joubuninaru | 丈夫になります joubuninarimasu | “becomes ~” — the change-of-state form. |
| Too much (~すぎる) | 丈夫すぎる joubusugiru | 丈夫すぎます joubusugimasu | “too ~”. |
| Looks ~ (~そう) | 丈夫そう joubusou | 丈夫そうです joubusoudesu | “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.