Only If (只有...才)

只有...才 states a necessary and exclusive condition. The structure is: 只有 + condition, 才 + result. It translates to "only if" or "only by doing X can Y happen." For example: 只有努力学习，才能考上好大学 — "Only by studying hard can you get into a good university."

This is stronger than a simple "if...then" (如果...就). 如果 presents a sufficient condition (if X happens, Y follows), while 只有 presents a necessary condition (X is the only way to get Y). Compare: 如果你努力，你就会成功 (If you work hard, you'll succeed — one possible path) vs. 只有你努力，你才会成功 (Only if you work hard will you succeed — the ONLY path).

才 in this pattern carries its core meaning of "only then / not until." It emphasizes that the result requires the stated condition. Without 才, the sentence loses its exclusive force.

Common variations include: 只有...才能 (only then can...), 只有...才会 (only then will...), 只有...才可以 (only then may...). The condition after 只有 can be a person, a thing, an action, or a circumstance.