Meaning
Vます＋合う expresses a reciprocal action: the participants do the same thing to each other (助け合う 'help each other') or jointly, exchanging (話し合う 'discuss', 意見を出し合う 'pool ideas'). The participants are a plural subject or 'A と B'. It is not the stand-alone verb 合う 'fit, match'.
Formation
- Group 1 verb: Vます＋合う: 話す → 話し合う (discuss)
- Group 2 verb: Vます＋合う: 助ける → 助け合う (help each other)
- する-verb — N＋し合う — 協力する → 協力し合う (cooperate with each other)
- Participants: AとBが／（私たちは）＋Vます＋合う: 兄と私がケーキを分け合う.
- 合う conjugates as a group 1 verb — 話し合った, 話し合って, 助け合おう, 助け合わない
When to use it
- Where to use it
- For mutual actions between people, groups or countries: 助け合う, 教え合う, 励まし合う, 連絡を取り合う, 意見を出し合う. Common in appeals: 困ったときは助け合おう.
- Where not to use it
- Grammar: you need at least two participants (a plural subject or と); the partner is not marked with に or を, and a one-way favour is expressed with ～てあげる／～てもらう. Style: 愛し合う and 信じ合う sound lofty; for everyday help around the house people usually just say 手伝う.
Examples
20 sentences-
困ったときは、お互いに助け合いましょう。
When times are hard, let's help each other out.
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週末の予定について、家族で話し合った。
We talked over the weekend plans as a family.
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兄と私は、一つのケーキを半分ずつ分け合った。
My brother and I split one cake between us, half each.
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二人は何も言わずに、じっと見つめ合っていた。
The two of them gazed at each other without a word.
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両国は、温暖化対策で協力し合うことにした。
The two countries agreed to cooperate with each other on climate measures.
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試験の前は、クラスのみんなで励まし合った。
Before the exam, everyone in the class cheered each other on.
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兄弟なのに、ほとんど連絡を取り合っていない。
We're brothers, yet we hardly keep in touch.
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日本語と英語を教え合う友達がいるんですか？
Do you have a friend you swap Japanese and English lessons with?
12 more examples
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会議では、若い社員も自由に意見を出し合っている。
In meetings, even the younger staff freely pitch ideas to one another.
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久しぶりに会った友達と、昔の話で笑い合った。
I met an old friend after ages, and we laughed together over old times.
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狭い道では、車同士が譲り合って通る。
On narrow roads, cars get through by giving way to each other.
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優勝が決まった瞬間、選手たちは抱き合って喜んだ。
The moment their victory was decided, the players hugged each other with joy.
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うちの両親は、いつもお互いを支え合っている。
My parents always support each other.
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チームのメンバーと、毎朝予定を確認し合っています。
Every morning my teammates and I go over our schedules with each other.
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子どもたちはおもちゃを取り合って、けんかを始めた。
The children grabbed the toy from each other and started a fight.
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失敗を責め合っても、何も解決しない。
Blaming each other for the failure won't solve anything.
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昔の友達と、今でも年賀状を送り合っていますか？
Do you still exchange New Year's cards with your old friends?
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これからもいいライバルとして、競い合っていこう。
Let's keep competing with each other as good rivals.
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友達と、旅行の写真を見せ合った。
My friends and I showed each other our travel photos.
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彼女とは、大学のサークルで知り合いました。
She and I got to know each other through a university club.
Important notes
- お互いに 'each other' often appears alongside it; this is normal reinforcement, not redundancy: お互いに励まし合う.
- Some combinations have become separate words: 話し合い 'discussion, talks', 付き合う 'go out with, keep company', 似合う 'suit (clothes)', 知り合う 'get acquainted'.
- サイズが合う, 意見が合う mean 'fit, match' with no ます-stem in front; Vます＋合う means a mutual action.
Common mistakes
- ✗ 友達と助けて合った → ✓ 友達と助け合った — 合う attaches to the ます-stem, not to the te-form.
- ✗ 彼は私を助け合った → ✓ 彼と私は助け合った (or 彼は私を助けてくれた) — with ～合う the partner is marked with と, not as a を-object.
- △ 私たちは意見が合った (meant 'we exchanged opinions') → 私たちは意見を出し合った／話し合った — 意見が合う means 'our opinions matched'.
Check yourself
Pick the translation of each sentence. The wrong options translate similar patterns, so watch the grammar rather than the words.
Similar grammar
- 〜てあげる～てあげる is a one-way action for someone else (助けてあげる); ～合う means both sides do the same thing for each other (助け合う).
- 〜てもらう～てもらう means receiving a favour from someone (教えてもらう 'have someone teach me'); ～合う is an exchange: 教え合う 'teach each other'.
- NとVN＋と＋verb just means 'with someone' (友達と話す 'talk with a friend'); ～合う adds reciprocity: 友達と話し合う 'discuss and settle with a friend'.
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