只有⋯⋯才⋯⋯
zhǐ yǒu …… cái ……
Expressing "only if" with "zhiyou"
只有…才… gives a necessary condition — it won't happen any other way.
只有 + Condition，才 + Result
How it works
只有你帮忙，我才能完成任务 — only with your help can I finish the job.
The pairing is fixed: 只要 goes with 就, 只有 goes with 才. Swapping them is a classic HSK 3 mistake.
只有 says this is the only route; 只要 says this route is enough.
Examples
zhǐ yǒu nǐ bāng máng, wǒ cái néng wán chéng rèn wu
只有你帮忙，我才能完成任务。
Only with your help can I finish the task.
zhǐ yǒu duō liàn xí, cái néng shuō hǎo zhōng wén
只有多练习，才能说好中文。
Only by practising a lot can you speak Chinese well.
zhǐ yǒu tā zhī dào mì mǎ
只有他知道密码。
Only he knows the password.
Common mistakes
- 只有 takes 才, never 就.