代える
かえる · kaeru · JLPT N3 · verb-ichidan
to exchange
代 means stand-in, as in 代理 proxy: kaeru = put a substitute in
Kaeru has several kanji. 変える means to change something. 換える means to swap one thing for another. 代える, with the 代 of 代理 (proxy) and 交代 (taking turns), means one thing takes over another's role, like a stand-in filling a slot.
代 — person radical 亻 + 弋 (stake/dart, phonetic)
代 is a semantic-phonetic compound: 亻 (person) gives the meaning and 弋 supplies the sound. The original sense was one person taking the place of another, which broadened to 'substitute,' 'replace,' and then 'generation' or 'era' — successive groups of people replacing the previous.