Every Japanese verb belongs to one of three groups. Identifying the group is the single most important thing you can know about a verb, because the group determines how the verb conjugates — past tense, polite tense, negatives, the te-form, and a dozen other forms all follow group-specific rules. Memorize the type when you memorize the meaning, and conjugation becomes mechanical.
Group 1 — u-verbs (五段, godan)
The largest group. The dictionary form ends in any kana of the う-row: う, く, ぐ, す, つ, ぬ, ぶ, む, る. They're called godan ("five steps") because they conjugate by sliding their final kana up and down the gojūon column.
| Verb | Reading | Meaning |
|---|---|---|
| 書く | kaku | to write |
| 話す | hanasu | to speak |
| 飲む | nomu | to drink |
| 買う | kau | to buy |
| 走る | hashiru | to run |
| ある | aru | to exist (inanimate) |
Notice that several u-verbs end in る. This is the trap of the system — you can't tell from the る ending alone which group a verb is in. More on that below.
Group 2 — ru-verbs (一段, ichidan)
Dictionary form ends in either いる or える. They're called ichidan ("one step") because conjugating them is dead simple — drop the final る and add whatever you're adding. No vowel shifting, no consonant changes.
| Verb | Reading | Meaning |
|---|---|---|
| 食べる | taberu | to eat |
| 見る | miru | to see, watch |
| 寝る | neru | to sleep |
| 起きる | okiru | to get up |
| いる | iru | to exist (animate) |
Anything that doesn't end in いる or える is automatically a u-verb — that's an absolute rule. The ambiguity only goes one direction.
Group 3 — Irregular verbs (不規則動詞)
Just two. They're so high-frequency that you'll meet them almost immediately, and they break the rules in idiosyncratic ways. Memorize their forms separately.
| Verb | Reading | Meaning |
|---|---|---|
| する | suru | "to do" — used to verb-ify nouns: 勉強する (to study) |
| 来る | くる (kuru) | "to come" — note the reading varies wildly across forms |
The verb する is enormously productive. Many nouns become verbs by tacking on する: 勉強 (benkyō, "studying") → 勉強する (to study). 運動 (undō, "exercise") → 運動する (to exercise). It's the equivalent of English's "do studying," "do exercise" — and it's everywhere.
The いる/える trap
A handful of common verbs end in いる or える but are u-verbs, not ru-verbs. They look like they should drop the る for conjugation, but they don't — they conjugate by shifting the final kana like other u-verbs.
| Verb | Reading | Group |
|---|---|---|
| 帰る | kaeru | u-verb (not ru!) — to return home |
| 切る | kiru | u-verb — to cut |
| 知る | shiru | u-verb — to know |
| 入る | hairu | u-verb — to enter |
| 走る | hashiru | u-verb — to run |
There's no rule that lets you predict these from the spelling alone. The only way to know is to learn the type at the same time you learn the verb. Yukimoji tags every verb with its group on the back of the card, so you'll always have it.
Why does the type matter?
Because every form of the verb depends on it. Take the polite form (the -masu form, which you'll use constantly):
| Group | Rule | Example: dictionary → polite |
|---|---|---|
| Ru-verb | Drop る, add ます | 食べる → 食べます |
| U-verb | Shift final kana to い-row, add ます | 書く → 書きます (kaku → kakimasu) |
| する | Memorize | する → します |
| 来る | Memorize (reading shifts!) | 来る (kuru) → 来ます (kimasu) |
And the negative form, and the past, and the te-form, and the potential, and the passive — all branch on the verb's group. Get the type wrong and every conjugation downstream is wrong.
Practical advice
When you encounter a new verb, your reflex should be: what group is this? A second of attention at lesson time saves a minute of confusion every time you hit a new conjugation form later. Yukimoji marks the type explicitly on the vocab card; pay attention to the marker, not just the meaning.
The next guide (Verb Conjugation) walks through the major forms with side-by-side tables for all three groups. If you're staring at a verb wondering "what does ました mean," that's the next stop.