To come together, merge, or join (for physical or abstract things) — to meet or unite at a point.
二つの川がこの地点で合う。
Two rivers meet at this point.
各部署が合って一つのチームとして動き始めた。
The departments came together and began operating as a single team.
地図上の線と実際の道が正確に合った。
The line on the map matched exactly with the actual road.
To fit, match, suit, or agree — for sizes, tastes, opinions, schedules, etc.
そのシャツはサイズがちょうど合う。
That shirt fits perfectly.
二人は趣味が合って、すぐに仲良くなった。
The two had matching hobbies and quickly became close.
来週の予定は君の都合と合うだろうか？
Will next week's schedule match your availability?
色の組み合わせが合っているね。
The color combination suits each other well.
To be profitable or worth the effort/cost — used in expressions like 割に合う (to be worthwhile).
この仕事は給料に比べて割に合わないと感じる。
I feel this job isn't worth the pay.
労力に見合う報酬が欲しい。
I want compensation that matches the effort.
An auxiliary/compound use attached to the -masu stem of a verb to mean 'to do ... to each other' or 'to do ... together' (e.g., 助け合う, 話し合う).
隣人と助け合って暮らしている。
We live helping each other with our neighbors.
意見を出し合って最終案を決めた。
We exchanged opinions and decided on the final plan.
困ったらみんなで話し合おう。
If there is a problem, let's all talk it over together.