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Japanese verb conjugation becomes predictable once you identify the verb group. Ichidan verbs usually drop る; godan verbs change their final kana row; and する and 来る are irregular. The chart below compares dictionary, polite, negative, past, te, potential, passive, causative, and conditional forms using one model verb from each group.
| Form | Godan: 書く | Ichidan: 食べる | Irregular: する | Irregular: 来る |
|---|---|---|---|---|
| Dictionary | 書く | 食べる | する | 来る |
| Polite | 書きます | 食べます | します | 来ます |
| Negative | 書かない | 食べない | しない | 来ない |
| Past | 書いた | 食べた | した | 来た |
| Negative past | 書かなかった | 食べなかった | しなかった | 来なかった |
| Te-form | 書いて | 食べて | して | 来て |
| Potential | 書ける | 食べられる | できる | 来られる |
| Passive | 書かれる | 食べられる | される | 来られる |
| Causative | 書かせる | 食べさせる | させる | 来させる |
| Conditional | 書けば | 食べれば | すれば | 来れば |
| Volitional | 書こう | 食べよう | しよう | 来よう |
Most verbs ending in an e-row or i-row sound plus る are ichidan, such as 食べる and 見る. Many other endings are godan. However, common exceptions such as 入る, 走る, 帰る, and 知る look like ichidan verbs but conjugate as godan.
| Signal | Likely group | Example | Warning |
|---|---|---|---|
| Ends in -eru or -iru | Often ichidan | 食べる / 見る | Check exceptions |
| Ends in -u, -ku, -gu, -su, -tsu, -nu, -bu, -mu | Godan | 書く / 話す / 読む | Final kana changes |
| Ends in suru | Suru verb | 勉強する | Conjugate suru |
| 来る | Irregular | 来る | Stem changes to こ / き / くる |
| Dictionary ending | Te-form | Past form | Example |
|---|---|---|---|
| う・つ・る | って | った | 買う → 買って |
| む・ぶ・ぬ | んで | んだ | 読む → 読んで |
| く | いて | いた | 書く → 書いて |
| ぐ | いで | いだ | 泳ぐ → 泳いで |
| す | して | した | 話す → 話して |
| 行く | 行って | 行った | Important exception |
Once the te-form is stable, patterns such as 〜ている, 〜てください, and 〜てもいい become much easier. Review the dedicated Japanese te-form guide for usage.
Beginner materials usually teach three groups: godan, ichidan, and irregular verbs. Suru compounds are handled with the irregular verb suru.
Learn dictionary, masu, negative, past, and te-form first. They unlock most beginner grammar.
Eru and iru endings are often ichidan, but common exceptions must be learned. A dictionary or trusted list is the safest check.
For ichidan verbs, the standard potential and passive forms both end in rareru. Context distinguishes the meaning.
Most conjugation is highly regular after group identification. Suru, kuru, and a few special forms require separate attention.
Choose five common verbs from different groups and produce each target form in a short sentence, then review mistakes with spaced repetition.
YoruLearn turns conjugation rules into fill-in-the-blank drills and adaptive review so forms return before you forget them.