Japanese verb conjugation basics: godan, ichidan, and irregular verbs

Japanese verb conjugation looks scary in a textbook, but the system underneath is remarkably tidy: there are exactly three verb groups, only two genuinely irregular verbs in the whole language, and no conjugation for person or number — 書く is 書く whether I write, you write, or they write. The one skill that unlocks everything is telling which group a verb belongs to. This guide teaches you that skill, walks through the six forms you need first, and flags the traps that catch almost every learner.

1. The three verb groups in 60 seconds

The names describe the mechanics. Godan means "five steps": to conjugate 書く you slide its last kana through the か-column — 書かない, 書きます, 書く, 書ける, 書こう. Ichidan means "one step": 食べる keeps the stem 食べ and simply swaps what comes after it — 食べない, 食べます, 食べられる, 食べよう. Compound verbs built with する (勉強する "to study", 練習する "to practice") conjugate exactly like する, so the irregular group is bigger in practice than its two members suggest.

2. How to identify a verb's group

1. If the dictionary form ends in anything other than る — that is, く, ぐ, す, つ, ぬ, ぶ, む, or う — it is godan, no exceptions. 書く, 泳ぐ (およぐ, swim), 待つ (まつ, wait), 飲む (のむ, drink), 買う (かう, buy) are all godan.
2. If it ends in る with an a, u, or o sound right before the る, it is also godan: 分かる (わかる, understand), 作る (つくる, make), 乗る (のる, ride).
3. If it ends in -eru or -iru, it is usually ichidan (食べる, 見る, 教える) — but a well-known set of godan verbs wears this disguise. Learn the trap list below.
4. する, 来る, and anything ending in する → irregular.

The -eru / -iru trap list

These common verbs end in -eru/-iru but are godan. Their ます-form gives them away: godan verbs keep the r sound (帰る → 帰ります), while ichidan verbs drop る entirely (食べる → 食べます).

Watch the homophone pairs: 帰る (go home, godan) vs 変える (change, ichidan), 切る (cut, godan) vs 着る (wear, ichidan), 要る (need, godan) vs 居る (exist, ichidan). Same sound, different group, different conjugation — 切ります but 着ます. When you meet a new -eru/-iru verb in the N5 or N4 word lists, check its ます-form once and the group is settled forever.

3. The six forms you need first — full walkthrough

These six forms cover the bulk of daily conversation and everything JLPT N5–N4 asks of you. Here they are for one model verb from each group (来る changes its reading as it conjugates — き, こ — even though the kanji stays the same):

Read the 食べる column top to bottom and you'll see why ichidan verbs are the easy group: drop る, attach the ending, done. The 書く column is where the "five steps" happen — か (negative), き (polite), け (potential), こ (volitional). する and 来る follow no pattern at all, but since there are only two of them, an evening with the review deck settles them for life.

The ます-form is really a family of four, all built on the same polite stem — learn them as a set: 書きます (present/future), 書きません (negative), 書きました (past), 書きませんでした (past negative). The same stem also takes たい for wants — 書きたい ("I want to write"), 食べたい ("I want to eat") — which is why textbooks drill the ます-form first: one stem, five everyday meanings.

4. Godan te-form: the sound-change rules (音便)

For godan verbs, the te-form and plain past don't use the vowel-shift — they use sound contractions that depend on the final kana. There are only four patterns plus one famous exception, and the same rule gives you both て and た (just swap the vowel: 書いて → 書いた):

The one exception every learner must memorize: 行く (いく, go) → 行って, 行った — not ×行いて. It behaves like the う/つ/る group despite ending in く.

5. A step-by-step recipe for any new verb

1. Classify it. Non-る ending → godan. る after a/u/o → godan. る after e/i → ichidan unless it's on the trap list. する/来る → irregular.
2. Find the stem. Ichidan: chop る (食べる → 食べ). Godan: shift the last kana to the い-row for the polite stem (飲む → 飲み).
3. Attach the ending. ます to the polite stem, ない to the あ-row stem (godan) or bare stem (ichidan), て/た by the sound-change table above.
4. Say the whole set out loud once. 飲む・飲みます・飲んで・飲んだ・飲まない・飲める・飲もう. Ten seconds of speaking cements a pattern far better than re-reading a chart.

One special case worth knowing early: for godan verbs ending in う, the negative uses わ, not あ — 買う → 買わない (kawanai), 会う → 会わない. And ある (to exist) has the irregular negative ない, not ×あらない.

6. Common learner mistakes

• Conjugating trap verbs as ichidan. ×帰て, ×帰ない, ×入れます ("enter"). Correct: 帰って, 帰らない, 入ります. This is the single most common conjugation error at N5 level.
• Forgetting 行く → 行って. If you catch yourself saying ×行いて, drill 行って・行った a few times in daily study sentences.
• Using を with potential verbs. Potential forms prefer が: 漢字が読める ("can read kanji"), not ×漢字を読める. Textbooks accept both in some cases, but が is the safe default.
• ら抜き shortcuts on the JLPT. In casual speech Japanese people often say 食べれる instead of 食べられる ("can eat"). Fine for conversation — but the JLPT and formal writing expect the full 〜られる for ichidan verbs and 来られる for 来る.
• Translating tense one-to-one from English. The た-form covers "did" and "have done"; the て-form plus いる covers ongoing states (住んでいる = "live", not "am living somewhere temporarily"). Learn forms with whole example sentences, not as isolated endings.

7. How to practice conjugation efficiently

Conjugation sticks when it rides on vocabulary you're already reviewing. Work through the JLPT N5 word list and, for every verb you meet, classify its group before flipping the card — that one-second habit trains the identification reflex. The word modules mark each entry's reading, so you can check trap verbs instantly, and the dictionary lets you confirm any verb you meet in the wild. Verbs you misclassify will naturally resurface via spaced review until they stop being traps. If you're just starting out, pair this guide with the N5 essential words guide — the ~120 verbs there cover the huge majority of everyday conjugation practice you'll ever need.