腐る (kusaru) conjugation
to rot, to go bad
腐る (くさる, kusaru) is a godan verb. Godan verbs change their final kana up and down its column of the kana chart — the a-row for negatives, the i-row before ます, the e-row for potential and ば. Every form below is tappable — hear it, then say it back.
Conjugation table
| Form | Plain (casual) | Polite (~ます) | When you use it |
|---|---|---|---|
| Dictionary / plain | 腐る kusaru | 腐ります kusarimasu | The form you look up. Also the casual present and future. |
| Plain negative | 腐らない kusaranai | 腐りません kusarimasen | “doesn’t / won’t”. From here it conjugates like an i-adjective. |
| Plain past | 腐った kusatta | 腐りました kusarimashita | The casual past — same ending as the te-form, with た/だ. |
| Plain past negative | 腐らなかった kusaranakatta | 腐りませんでした kusarimasendeshita | “didn’t”. The negative past, still i-adjective-shaped. |
| Te-form | 腐って kusatte | — | The connector: requests, linking clauses, ~ている. |
| Progressive (~ている) | 腐っている kusatteiru | 腐っています kusatteimasu | “is ~ing”, or an ongoing resulting state. |
| Desire (~たい) | 腐りたい kusaritai | 腐りたいです kusaritaidesu | “want to ~”. Behaves as an i-adjective. |
| Volitional | 腐ろう kusarou | 腐りましょう kusarimashou | “let’s ~” / “I think I’ll ~”. |
| Potential | 腐れる kusareru | 腐れます kusaremasu | “can ~”. What you could do; the object often takes が. |
| Passive | 腐られる kusarareru | 腐られます kusararemasu | “is ~ed”. Also the honorific and the suffering passive. |
| Causative | 腐らせる kusaraseru | 腐らせます kusarasemasu | Make or let someone do it. |
| Causative-passive | 腐らされる kusarasareru | 腐らされます kusarasaremasu | Be made to do it — the long one. |
| Imperative | 腐れ kusare | 腐ってください kusattekudasai | Blunt order. Use ~てください in real life. |
| Prohibitive | 腐るな kusaruna | — | “don’t!” — dictionary form + な. |
| Conditional (~ば) | 腐れば kusareba | — | “if ~”. General rules and hypotheticals. |
| Conditional (~たら) | 腐ったら kusattara | — | “if / when ~”. The everyday conditional. |
🔊 Tap any Japanese word to hear it spoken.
Why it conjugates this way
Godan verbs change their final kana up and down its column of the kana chart — the a-row for negatives, the i-row before ます, the e-row for potential and ば.
See the full rules on the verb conjugation guide.