化学(huà xué) - chemistry in Mandarin

化学 (huàxué) is chemistry, the school subject and the science. 化 (huà) on its own means "to change, to transform", and 学 (xué) means "study", so the compound reads literally as "the study of transformation", a fair description of what happens in the subject.

It sits alongside the other sciences in the school timetable: 物理 (wùlǐ) is physics and 生物 (shēngwù, from sheng1-wu4) is biology. If you are talking about your options at 高考 (gāokǎo), the university entrance exam, 化学 is one of the three sciences learners weigh up alongside the humanities.

English speakers rarely trip over the pronunciation, but the tones are worth drilling: 化 (huà) is falling, 学 (xué) is rising, and running them together fast is what marks out a natural speaker rather than someone reading off a vocabulary list.