除非

In a sentence

• 除非你努力学习，否则你不会通过考试。

  Unless you study hard, you will not pass the exam.

  Here, '除非' introduces a condition for the proposition to follow, paired with '否则' indicating the alternative.

• 我平时很少吃甜点，除非是有人生日。

  I rarely eat desserts unless it's someone's birthday.

  In this sentence, '除非' is used to indicate an exception to the general statement.

• 我们不出门，除非雨停了。

  We won't go out unless the rain stops.

  The usage of '除非' marks a specific condition that must be met for the future action to take place.