用于
yòng yú · HSK 5
use for
🛠️ 用 = use + 于 = at/in/on → 'used at/for'
用 means 'to use' and 于 is a classical preposition meaning 'at, in, on, for'. Together 用于 marks the purpose or domain something is applied to, like saying 'used for/in [X]'.
用 — pictograph of a bucket or wooden pail
用 originally depicted a bucket or container, possibly a sacrificial vessel made of wood. Over time it was borrowed to mean 'to use' or 'employ,' losing its concrete object sense. The modern meaning 'use' has been standard since early classical Chinese.
于 — two horizontal strokes 二 + vertical hook 亅
于 originated as a pictograph of breath or sound flowing outward, depicting exhalation through a passage. In oracle bone script it resembled a curved line showing motion or extension. Over time it became a grammatical preposition meaning 'at,' 'in,' or 'to,' losing its original concrete sense.