組合
くみあい · kumiai · JLPT N3 · noun
union
🧩🤝 組 kumi (group, braid) + 合 ai (fit together) = people joined into a union
組 comes from kumu, to braid or assemble, and 合 comes from au, to fit or meet. So a 組合 is people woven together into one group. You will often see it in 労働組合 (rōdō kumiai, labour union) and 協同組合 (kyōdō kumiai, co-op).
合 — 乛 (lid/roof) + 口 (mouth)
Originally a pictograph of a lidded vessel — a cover (亼) closing over an opening (口) — giving the core sense of 'come together, join, fit.' From 'fit/match' it extended to 'combine, unite, agree' and to measure-word uses. The reading hé reflects this 'joining' meaning.