unless

conj.

1. 除非；除非在…情况下
   used to say that sth can only happen or be true in a particular situation
   1. You won't get paid for time off unless you have a doctor's note.
      除非你有医生证明，否则你不上班便拿不到工资。
   2. I won't tell them─not unless you say I can.
      我绝不告诉他们——除非你允许。
   3. Unless I'm mistaken, she was back at work yesterday.
      除非是我记错了，她是昨天回来上班的。
   4. He hasn't got any hobbies─unless you call watching TV a hobby.
      他没有什么爱好——除非你把看电视也称作爱好。
2. 若非；如果不
   used to give the only situation in which sth will not happen or be true
   1. I sleep with the window open unless it's really cold.
      天气若不很冷，我总开着窗户睡觉。
   2. Unless something unexpected happens, I'll see you tomorrow.
      如果不出意外，我明天去看你。
   3. Have a cup of tea─unless you'd prefer a cold drink?
      喝杯茶吧——除非你喜欢冷饮？

1. CONJ-SUBORD 除非；若不；除非在…的时候
   You use unless to introduce the only circumstances in which an event you are mentioning will not take place or in which a statement you are making is not true.
   1. Unless you are trying to lose weight to please yourself, it's going to be tough to keep your motivation level high...
      除非减肥是为了悦已，否则很难保持积极性。
   2. We cannot understand disease unless we understand the person who has the disease...
      若不了解患者我们就不能了解疾病。
   3. I'm not happy unless I ride or drive every day.
      只有每天骑车或开车我才会开心。

Do not confuse unless, except, except for, and besides. Unless is used to introduce the only situation in which something will take place or be true. In the 1940s, unless she wore gloves a woman was not properly dressed... You must not give compliments unless you mean them. You cannot use unless to talk about a situation that results from something not happening. Instead you use if...not. I'll be glad if she doesn't come. You use except to introduce the only things, situations, people, or ideas that a statement does not apply to. All of his body relaxed except his right hand... Travelling was impossible, except in the cool of the morning. You use except for before something that prevents a statement from completely true. The classrooms were silent, except for the scratching of pens on paper... I had absolutely no friends except for Tom. You use besides to introduce extra things in addition to the ones you are mentioning already. Fruit will give you, besides enjoyment, a source of vitamins. However, note that if you talk about 'the only thing' or 'the only person besides' a particular person or thing, besides means the same as 'apart from'. He was the only person besides Gertrude who talked to Guy.
不要混淆 unless，except，except for 和 besides。unless用于引出某事发生或成立所必需的条件，如：In the 1940s, unless she wore gloves a woman was not properly dressed（在20世纪40年代，女性若不戴手套就算衣着不得体），You must not give compliments unless you mean them（除非出自真心，否则不要随便恭维）。谈论由于某事未发生而导致的情形不能用unless，要用 if...not，如：I'll be glad if she doesn't come（如果她不来我会很高兴的）。except 用于引出陈述中唯一不适用的事物、情形、人或想法，如：All of his body relaxed except his right hand（除了右手以外，他全身都放松了），Travelling was impossible, except in the cool of the morning （除了在凉爽的早晨，其他时候出行都是不可能的）。except for用于引出使其陈述不能完全成立的事物，如：The classrooms were silent, except for the scratching of pens on paper（除了笔在纸上发出的沙沙声，教室一片寂静），I had absolutely no friends except for Tom（除了汤姆，我一个朋友也没有）。besides用于引出已提到事物之外的其他事物，如：Fruit will give you, besides enjoyment, a source of vitamins（水果不但好吃，而且富含维生素）。但应注意，用于谈论除某人或某物之外唯一的人或物时，besides的意思与apart from相同，如：He was the only person besides Gertrude who talked to Guy（除格特鲁德之外，他是唯一跟盖伊说话的人）。

1. The man in the store won't give him change for the phone unless he buys something.
   店里的人不肯给他换硬币打电话，除非他买点什么。
2. Leave your cheque book and credit cards at home unless you know you will need them.
   除非确实需要用到支票簿和信用卡，否则别带在身上。
3. He had realized that Britain could not have peace unless she returned at least some of her former conquests.
   他意识到除非英国至少归还一部分以前的占领地，否则国无宁日。
4. You're not going to get out of here unless we make a deal.
   除非我们达成协议，否则你就别想从这儿出去。
5. Unless she loses some weight, she's had it
   除非她减点儿肥，否则她就没戏了。
6. Such schemes mean little unless they impact on people.
   这些计划没什么意义，除非它们对人民产生影响。
7. People don't just knock one another off like this unless there's big money at stake.
   如果不是为了冒险赚大钱，人们不会像这样彼此残杀。
8. I tend to forget things unless I mark them down
   除非把事情记下来，否则我常常会忘事。
9. The ship may be heading for the metaphorical rocks unless a buyer can be found.
   除非可以找到买家，否则这条船也许就像朝着岩石撞过去一样下场悲惨。
10. She refused to testify, unless the murder charge against her was dropped.
    除非撤销对她的谋杀指控，否则她拒绝作证。
11. Her bank warned that unless she repaid the overdraft she could face legal action.
    银行警告她如果不偿还透支钱款，她将面临诉讼。
12. No-one could use the computer unless they had a password.
    除非知道密码，否则谁也用不了那台计算机。
13. Unless these questions are solved, the region will remain a powder keg.
    除非这些问题得到解决，否则该地区会一直是个火药桶。
14. There is no point in pushing them unless they are talented and they enjoy it.
    除非他们很有才华而且自己喜欢，否则逼迫他们是没有意义的。
15. They're going to be famous, but unless something happens, they're going to self-destruct
    他们将会出名，但如果照现在这样发展下去，他们会自毁前程。
16. The conservatory will get very hot in summer unless shading is used.
    夏天如果不用遮光罩的话，暖房会变得特别热。
17. All bitches should be spayed unless being used for breeding.
    除非是用作种犬，所有的母犬都应摘除卵巢。
18. Unless you are trying to lose weight to please yourself, it's going to be tough to keep your motivation level high
    除非减肥是为了悦已，否则很难保持积极性。
19. We cannot understand disease unless we understand the person who has the disease
    若不了解患者我们就不能了解疾病。
20. I'm not happy unless I ride or drive every day.
    只有每天骑车或开车我才会开心。
21. Why did you need a room unless you were up to something?
    除非你要搞什么小动作，不然你为什么单要一间房？
22. Avoid changing a nappy unless it's dirty or very wet.
    除非尿布脏了或非常湿，否则别换。
23. There's no snake known that will habitually attack human beings unless threatened with its life
    除非自己的生命受到了威胁，已知的蛇中还没有习惯性地攻击人类的。
24. He won't stop drinking unless he's told by a doctor that it's killing him.
    除非医生告诉他喝酒会要他的命，否则他是不会戒酒的。
25. Don't take this medicine unless it's absolutely necessary.
    非万不得已不要用这种药。
26. We can't keep abreast of the developing situation unless we study harder.
    我们如果不加强学习，就会跟不上形势。
27. How can you expect to win confidence of the people unless you come to them with clean hands.
    你如何能赢得人民的信任，除非你以廉洁之身和他们打交道。
28. We shall simply be resigning ourselves to extinction unless we carry on the four modernizations.
    如果不搞四个现代化，我们就只有束手待毙。
29. We will not attack unless we are attacked; if we are attacked, we will certainly counterattack.
    人不犯我，我不犯人；人若犯我，我必犯人。
30. He'll never pay up unless you get tough with him.
    你如果不对他硬点，他是决不会把钱付清的。