Japanese verb groups, and why you need to tell them apart

Japanese verbs fall into three groups, and every conjugation depends on which group a verb is in. Get the group wrong and the て-form, the past, the negative and everything built on them come out wrong.

The good news: Japanese conjugation is extremely regular. Once you can identify the group, there is almost nothing to memorise.

The three groups

Group 1 — う-verbs (五段). The largest group. In the ます-form, the sound before ます is in the い row: かいます, いきます, のみます, はなします.

Group 2 — る-verbs (一段). In the ます-form, the sound before ます is in the え row or the い row and the dictionary form ends in る: たべます, みます, おきます.

Group 3 — irregular. There are two: します (to do) and きます (to come). That is the entire list.

Telling groups 1 and 2 apart

This is the only real difficulty, and there is a reliable test from the ます-form.

Look at the sound immediately before ます.

• If it is in the え row (え, け, せ, て, ね, へ, め, れ) → Group 2. たべます, みせます, ねます.
• If it is in the い row (い, き, し, ち, に, ひ, み, り) → usually Group 1. かいます, かきます, のみます.

The exception: a number of common verbs have an い-row sound before ます and are Group 2 anyway. There is no rule for these; they must be learned individually. The frequent ones:

• みます (see)
• おきます (get up)
• きます (wear)
• おります (get off)
• できます (can do)
• あびます (bathe)
• かります (borrow)

Learn that short list as exceptions and the test works almost everywhere else.

Why it matters

Take the て-form, which is where most beginner grammar attaches:

Group	Rule	Example
1	Endings vary by final sound	かいます → かって
2	Drop ます, add て	たべます → たべて
3	Irregular	します → して, きます → きて

Group 2 is trivial. Group 1 requires the ending rules. So misidentifying a Group 2 verb as Group 1 produces a wrong form every time, in every tense.

The same split governs the past (た-form), the negative (ない-form), the potential, the passive and the causative. One classification, applied everywhere.

How to learn it

Record the group when you learn the verb. Not later. Every new verb goes into your vocabulary system with its group attached, from the first day.

Drill aloud, in batches. Take twenty verbs, produce their て-forms out loud, check, repeat over several days. The goal is reflex, not knowledge.

Learn the Group 2 exceptions as a set. The list above is short and it covers most of what you will meet.

Do not conjugate by consulting rules. Nobody speaks that way. The rules are scaffolding for the first fortnight; after that it should be automatic.

Where it matters for exams

JFT-Basic needs the て-form, the ない-form and the past reliably, at listening speed. See the grammar you need.

JLPT N4 is substantially a test of whether this has become automatic. See the N4 guide.

And once groups are secure, the て-form — the single most useful thing in beginner Japanese — costs you very little.