unless

conj.

1. 除非, 如果不
   • You will fail unless you work hard.
     如果你不积极工作, 就会失败。
   • Let's have dinner out — unless you are too tired.
     咱们出去吃饭吧——除非你太累了。
   • Substances have no tendency to expand unless (they are) heated.
     除非受热, 物质不会有膨胀的倾向。
   • I will be very angry unless you have already spoken to her.
     除非你已经对她说过了, 否则我会很生气。
   • Don't ask me to explain unless you really don't understand.
     不要叫我解释, 除非你真的不懂。
   • Unless paying by credit card, please pay in cash.
     如果不用信用卡付账, 就请付现金。