合同
ごうどう · goudou · JLPT N2 · noun
combination
🧩 合 (join) + 同 (together): joining together into one whole = combination
合 means join or unite, and 同 means together or the same. Put them side by side and you get pieces brought together, the idea behind incorporation. Japanese uses it for joint events like 合同練習, a joint practice.
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.
同 — 冂 enclosure + 一 + 口 mouth
Originally depicted multiple mouths gathered under one cover or enclosure, suggesting people speaking together in agreement. From this image of voices joining, it came to mean 'same,' 'together,' or 'alike.' The shared cover symbolizes unity.