Verb conjugation

The one idea

Every Japanese verb form is a stem plus an ending. Nothing is memorised whole — you build it.

What separates the classes is only how many stems they have:

• Ichidan verbs have one stem. Drop る, attach anything.
• Godan verbs have five, one per vowel row. Pick the row the ending wants.
• する and くる change their own vowel too, and are the only two that do.

So learning verbs is really two jobs: work out which class a verb is in, then learn which stem each ending attaches to. There is no third job.

Which class is a verb in?

Only verbs ending in る are ever ambiguous. Everything else is decided for you.

• Doesn't end in る → godan. No exceptions. (のむ, かく, はなす, まつ, あそぶ)
• Ends in る, and the sound before it is a, u, or o → godan. No exceptions. (つくる, ある, とる)
• Ends in る, and the sound before it is i or e → usually ichidan, and this is the only case worth memorising. (たべる, みる, おきる)

The -iru / -eru verbs that are godan anyway

Short list, and it's worth knowing cold — these are common verbs.

A quick way to check one you're unsure of: put it in the negative. Ichidan drops る（たべる → たべない）; godan shifts to the a-row and keeps the consonant（はしる → はしらない）. If はしらない sounds right and はしない sounds wrong, it's godan.

The five stems

A godan verb shifts its final syllable through the five vowel rows. That's the whole system, and the name 五ご段だん means "five levels."

Take いく:

のむ behaves identically: のまない, のみます, のむ, のめば, のもう.

Ichidan verbs skip all of this. たべる drops る and every ending attaches to たべ: たべない, たべます, たべれば, たべよう.

The て-form

The て-form is the one place godan verbs don't simply follow the vowel rows, because the sounds wore down over time. It's five groups, sorted by the last kana of the dictionary form.

Ichidan needs no rule at all — drop る, add て: たべる → たべて, みる → みて.

And the two irregulars: する → して, くる → きて.

The た-form is free

Here's the part worth knowing before you memorise anything else: the past tense uses exactly the same rule as the て-form. Swap て for た, で for だ. That's it.

So the five groups above are not a て-form rule — they're a rule you use twice. Learn them once and the past tense costs you nothing.

It pays a third time, too: たら conditionals are just the た-form plus ら（いったら = if I go）, and たり is the た-form plus り.

Every other form

Once the stems and the て-form are in place, the rest is assembly.

Read down the godan column and you'll see the stems doing the work: いき+ます, いか+ない, いけ+ば, いこ+う. Only the past and て-form need the sound-change table.

Plain and polite

Every verb has four basic forms, and each exists twice — once plain, once polite. Eight cells, and you already have the pieces for all of them.

The polite column is entirely regular: it's the i-stem plus ます, ません, ました, ませんでした. No sound changes, ever. Even いく — the verb that breaks the て-form — is perfectly regular here: いきます.

What the て-form unlocks

The て-form isn't a tense. It's a connector — it hands the verb to something else, which is why it's worth the effort of learning the sound changes.

ている is the one to get right early. With action verbs it's a progressive（たべている = is eating）, but with verbs describing a change it's a resulting state, not an action in progress.

This also explains a form that surprises everyone: "I don't know" is しりません／しらない, never ✕しっていません. The positive しっている is a state, but Japanese drops back to the plain negative of しる to say you are not in it. しりません is the polite default; しらないです exists and is fine in casual-polite speech, just less polished.

Potential, volitional, imperative

Three forms that come straight off the stems, with no sound changes to learn.

Potential — can do

Potential verbs are themselves ichidan, so they keep conjugating: いける → いけない, いけた, いけて.

And the object usually takes が rather を: にほんごがはなせる.

Volitional — let's, shall we

The polite version is simply ましょう off the i-stem: いきましょう. And + とおもう makes it an intention rather than an invitation: いこうとおもう = I think I'll go.

Imperative — do it

Blunt. Real, but it carries weight — you'll hear it in orders, signs, sports and anger more than in conversation.

For everyday requests, use てください or the softer なさい（i-stem + なさい: たべなさい）, which is what a parent or teacher says.

Passive and causative

Both attach to the a-stem for godan verbs, and both produce new ichidan verbs — so everything you already know keeps applying to the result.

Passive — was done to me

Japanese also uses the passive where English wouldn't — to say something happened to your detriment: あめにふられた, literally "I was rained on."

Causative — make or let someone do

Whether it means make or let comes from context and particle: を tends toward making someone, に toward letting them.

Causative-passive — was made to do

Stack them: causative, then passive. いかせる → いかせられる = was made to go.

Godan verbs usually contract this to される: いかされる.

Four ways to say "if"

All four translate as "if" or "when," and they are not interchangeable.

たら is the safest default when you're unsure — it accepts the widest range of situations.

Adjective and noun conditionals（さむければ, しずかなら, がくせいなら）are on the reference page.

と is the one that gets misused. It can't be followed by a request, a command, or an intention, because it describes something automatic.

なら is the only one that can attach to something the other person just said — which is why it so often opens a reply.

Adjectives conjugate too

Japanese adjectives carry tense, which English ones don't. さむかった is a single word meaning "was cold" — no verb involved.

Which pattern a word follows depends on its class: い-adjectives conjugate like verbs, な-adjectives conjugate like nouns — they borrow だ／です to do it.

い-adjectives — さむい

Notice the polite column never changes the word — です is bolted on afterwards, because さむい already carries the tense itself.

な-adjectives — しずか

Identical to how a noun behaves: がくせいだ, がくせいじゃない, がくせいだった. That's the whole point of the class.

The other forms, side by side

One pattern runs through that entire table: い-adjectives drop the い, な-adjectives use the bare stem. さむい loses its い to become さむく, さむくて, さむすぎる, さむそう. しずか simply takes に, で, すぎる, そう as it is.

いい is the one irregular

いい reverts to its older form よい the moment it conjugates.

Anything built on いい inherits this: かっこいい → かっこよかった, きもちいい → きもちよかった.

Traps checklist

The ある one catches everyone. ある is godan and conjugates normally everywhere else — あります, あって, あった — but its negative is suppletive: it's simply ない.

Why the て-form changed

Optional, but it turns an arbitrary table into three sound changes you can hear.

Originally every godan verb formed て off the i-stem, exactly like ます does — かき + て, のみ + て, かい + て. Then fast speech wore the middle down. Japanese calls this 音おん便びん, "sound convenience."

う-verbs did the same thing by a longer road: かう was once かふ, so かひ + て → かうて → かって. That is why かう and まつ and とる all land on って.

す verbs never changed because し + て was already easy to say — which is why はなして looks so regular next to the others.

It also explains the voicing. で and だ appear exactly where ん appears, because a nasal voices the consonant after it. のんで, あそんで, しんで — and およいで, where the ぐ left its voicing behind as it dropped.

The same wearing-down produced さむかった from さむく + あった, which is why adjectives and verbs both have a past tense full of small っ.

Verbs worth knowing

Ichidan

Godan

Irregular

する is also how Japanese turns nouns into verbs: べんきょう（study）→ べんきょうする, そうじ（cleaning）→ そうじする. Anything in that shape conjugates exactly like する.