石油
shíyóu · HSK 3
crude oil
🛢️ 石 (stone/rock) + 油 (oil) = rock oil = petroleum
Literally rock-oil: the oil that comes out of rock. English crude oil and rock oil are old synonyms for the same thing. 石 carries the stone/rock sense across many compounds.
油 — water radical 氵 + 由 (yóu, phonetic)
油 is a phono-semantic compound. The 氵 radical signals a liquid, while 由 supplies the sound. Originally referring to a river name, it was extended to mean oil or fat — any thick, flowing liquid — which became its dominant modern sense.