除非
chúfēi
unless
conjunction
Example
除非你努力学习，否则很难通过考试。
Chúfēi nǐ nǔlì xuéxí, fǒuzé hěn nán tōngguò kǎoshì.
Unless you study hard, it will be difficult to pass the exam.
A useful conditional conjunction often paired with 否则 (fǒuzé, 'otherwise'). It introduces a necessary condition for avoiding an undesirable outcome.