auxiliary N3 common casualpolitewritten
〜合う — to do ~ to each other
〜合う ・ あう
Builds on 連用形（ます形）
Meaning
- do ~ to each other / do ~ together (mutually) — two or more people direct the action at one another
Key sentence
二人は将来について話し合った。
The two of them talked things over about the future.
Formation
| Attaches to | Form | Example |
|---|---|---|
| Verb (masu-stem) | V(stem) + 合う | 助ける → 助け合う / 愛する → 愛し合う / 殴る → 殴り合う |
Examples
困ったときは家族で助け合う。
When times are hard, our family helps one another.
学生たちは答えを見せ合っていた。
The students were showing each other their answers.
二人は長い間見つめ合っていた。
The two gazed at each other for a long while.
When you can't use it
- The action must be mutual, so the subject is plural or joined by と — two or more parties acting on each other. A single person can't 話し合う alone; one person simply 話す.
Easily confused with
Notes
- Often reinforced by お互いに ('mutually') for emphasis: お互いに助け合う. Note this 〜合う is the reciprocal suffix, distinct from the standalone verb 合う ('to fit / to match').
See 〜合う in real sentences
Jengo shows 〜合う the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled from published Japanese grammar references.