結合
けつごう · ketsugou · JLPT N1 · noun
combination
🔗 結 = tie + 合 = join: 結合 means tying parts together so they join as one
結 (ketsu) means tie or bind, and 合 (gou) means meet or fit together. Tying two parts so they fit as one gives 結合, a combination or union.
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.