合うMutual or joint action
Attach 合う to a verb stem to show that two or more participants perform the action toward one another or carry it out together.
Two closely related readings
The action may be clearly reciprocal, as when people acknowledge or look at one another. It may instead be collaborative, as when people discuss an issue together. In either case, the compound presents the participants as connected through one shared action.
Reciprocal and collaborative actions
二人は最後まで互いの意見を認め合った。
The two acknowledged each other's views to the end.
AnalyzeEach person directs the action toward the other, so the meaning is reciprocal.
チームは新しい企画について何度も話し合った。
The team discussed the new project several times.
Analyze話し合う conventionally means to discuss something together, not merely to speak to one another.
Who performs the action?
The meaning requires at least two participants. They may be named separately, expressed by a plural or collective noun, or simply understood from the situation. A grammatically singular subject can therefore work only when its partners are clear from context.
姉と私は試験の前に励まし合った。
My sister and I encouraged each other before the exam.
AnalyzeThe two participants are stated explicitly.
Changing the whole compound
兄と弟は子供のころ、物を貸し合わなかった。
When they were children, the older and younger brothers did not lend things to each other.
AnalyzeThe negative ending is attached to the final 合う part of the completed compound.
Naming the participants versus describing the action
同士 identifies people or things as members of the same group. It does not itself make an action reciprocal; the verb ending in 合う expresses what those participants do together or to one another.
同じ部署の社員同士で意見を出し合った。
Employees in the same department exchanged ideas with one another.
Analyze社員同士 identifies the participants, while 出し合った expresses their shared action.
More examples
学生たちは書いた答えを見せ合った。
The students showed one another the answers they had written.
Analyze問題が起きたときこそ、みんなで助け合うことが大切だ。
It is especially important for everyone to help one another when problems arise.
Analyze会議では遠慮せずに意見を出し合いましょう。
At the meeting, let us share our ideas without holding back.
Analyze二人はしばらく黙って見つめ合っていた。
The two of them silently looked into each other's eyes for a while.
Analyze失敗しても、責任を押し付け合ってはいけない。
Even when something goes wrong, you must not shift the blame onto one another.
Analyzeオンラインでも参加者同士が学び合える。
Participants can learn from one another even online.
Analyze