'只有' (zhǐ yǒu) is a two-character conjunction/adverb meaning 'only if' or 'only' — it expresses a necessary condition or exclusivity. Literally, '只' means 'only' or 'just', and '有' means 'to have' or 'there is'; together they convey the idea that something exists or occurs *only when* or *only under the condition that* something else is true. It often introduces the sole prerequisite for an outcome.

This expression commonly appears at the beginning of a clause, followed by a verb phrase or sentence, and then a main clause introduced by '才' (cái), '就' (jiù), or '能' (néng) to show the result — though it can also stand alone in simple statements of exclusivity. It's neutral in register and widely used in both spoken and written Chinese, especially in logical, causal, or restrictive contexts like rules, warnings, promises, or factual statements.