新陈代谢
xīn chén dài xiè · HSK 7
metabolism
🔄 新陈代谢 = new (新) + stale (陈) + replace (代) + shed (谢): new replaces old
Each character builds the idea: 新 new, 陈 stale/aged, 代 to substitute, 谢 to wither or fall away. Together they name the body swapping fresh material for spent — metabolism — and the figurative sense of the new displacing the outworn.
新 — 立 stand + 木 tree + 斤 axe
Originally depicted cutting fresh wood with an axe (斤) from a tree (木), with 辛/立 as the phonetic component. The original meaning of 'firewood' was later written as 薪, while 新 took on the extended sense of 'new' or 'fresh'.
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.