解答
かいとう · kaitou · JLPT N2 · noun
answer
🔑 解 (untie, solve) + 答 (answer) = kai-tou: the answer that unties the problem
解 means untie or solve, and 答 means answer. Untying the knot of a problem gives the solution, which is what 解答 names.
解 — horn 角 + knife 刀 + ox 牛
解 is an ideograph showing hands using a knife (刀) to separate the horn (角) from an ox (牛). The original meaning was to butcher or dismember an ox, which broadened to 'untie, separate, loosen,' and then extended figuratively to 'explain' or 'understand'—to take something apart mentally.
答 — bamboo radical 竹 + 合 (combine)
Originally written with the bamboo radical because answers were inscribed on bamboo slips. The phonetic 合 ('to join, match') gives both the sound and the sense of a reply 'matching' a question. Over time 答 came to mean 'answer' or 'respond' generally.