除非【chúfēi】

除非 names the only condition under which things turn out differently. The condition follows 除非, and the second half needs a word to say which way it turns: 才 for "only if", 不然 or 否则 for "unless".

除非…才: "only if"

With 才, the second half is what happens, and it happens only under that condition. 才 goes after the subject, before the verb.

除非…不然 / 否则: "unless"

With 不然 or 否则, the second half is what happens if the condition isn't met. 否则 is more formal.

The 除非 clause can also come second, as an afterthought, with nothing added to the first half.

Translating "unless"

The condition after 除非 is what has to happen for things to change. English "unless" already contains a "not", so carrying a 不 over from "I won't go unless you go" turns the condition upside down. The second half still needs its 才, 不然 or 否则.

• × 除非你不去，我不去 → 除非你去，我才去
• × 除非你去，我去 → 除非你去，我才去

除非…否则 in formal writing has its own point.