徹する (tessuru) conjugation
to devote oneself, to believe in
徹する (てっする, tessuru) is an irregular verb. Only する and 来る are truly irregular, and every learner meets them in week one. 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 | 徹する tessuru | 徹します tesshimasu | The form you look up. Also the casual present and future. |
| Plain negative | 徹しない tesshinai | 徹しません tesshimasen | “doesn’t / won’t”. From here it conjugates like an i-adjective. |
| Plain past | 徹した tesshita | 徹しました tesshimashita | The casual past — same ending as the te-form, with た/だ. |
| Plain past negative | 徹しなかった tesshinakatta | 徹しませんでした tesshimasendeshita | “didn’t”. The negative past, still i-adjective-shaped. |
| Te-form | 徹して tesshite | — | The connector: requests, linking clauses, ~ている. |
| Progressive (~ている) | 徹している tesshiteiru | 徹しています tesshiteimasu | “is ~ing”, or an ongoing resulting state. |
| Desire (~たい) | 徹したい tesshitai | 徹したいです tesshitaidesu | “want to ~”. Behaves as an i-adjective. |
| Volitional | 徹しよう tesshiyou | 徹しましょう tesshimashou | “let’s ~” / “I think I’ll ~”. |
| Potential | 徹できる teddekiru | 徹できます teddekimasu | “can ~”. What you could do; the object often takes が. |
| Passive | 徹される tessareru | 徹されます tessaremasu | “is ~ed”. Also the honorific and the suffering passive. |
| Causative | 徹させる tessaseru | 徹させます tessasemasu | Make or let someone do it. |
| Causative-passive | 徹させられる tessaserareru | 徹させられます tessaseraremasu | Be made to do it — the long one. |
| Imperative | 徹しろ tesshiro | 徹してください tesshitekudasai | Blunt order. Use ~てください in real life. |
| Prohibitive | 徹するな tessuruna | — | “don’t!” — dictionary form + な. |
| Conditional (~ば) | 徹すれば tessureba | — | “if ~”. General rules and hypotheticals. |
| Conditional (~たら) | 徹したら tesshitara | — | “if / when ~”. The everyday conditional. |
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Why it conjugates this way
Only する and 来る are truly irregular, and every learner meets them in week one.
See the full rules on the verb conjugation guide.