考试

考试 (kǎoshì) means both 'exam' (the noun) and 'to take an exam' (the verb-object compound). It's a separable verb-object construction: 考 ('to test') + 试 ('a trial / test'). To say 'take an exam' you can use 考试 directly (我明天考试 'I have an exam tomorrow') or split it for an object — 考一个试 ('take a test'), 考英语试 is wrong; instead say 考英语 or 英语考试. Closely related: 考 alone is the active verb 'to take a test in / to test someone' — 考英语 ('take an English exam'), 老师考我们 ('the teacher tests us'). Exams shape Chinese student life: 高考 (gāokǎo) is the national college entrance exam, 中考 the high-school entrance one, 期末考试 the final exam. To pass is 通过考试 or 考过; to fail is 不及格 or 没考过. The character 考 also means 'to consider / examine' (考虑 'consider').

Memory hook: 考 (test) + 试 (try) — a 'testing trial.' Both characters mean a kind of test, doubled to nail down the meaning.