How to Use UNLESS in Conditional Sentences
UNLESS引导的条件状语从句
◆ UNLESS means something similar to EXCEPT IF or IF…NOT. The clause which follows UNLESS is a subordinate clause: it needs a main clause to make a complete sentence.
◆ UNLESS在引导条件状语从句时，与EXCEPT IF/IF…NOT意思相近。UNLESS引导的是从句，所以需要一个主句来构成一个完整的句子。
◆ Note that in clauses with IF and UNLESS, we use a present tense to refer to the future. So, we don’t use WILL/WOULD in the UNLESS subordinate clause.
◆ UNLESS引导条件状语从句时，跟IF引导条件状语时相同，遵循主将从现原则，即主句用将来时，UNLESS从句用一般现在时表将来。因此UNLESS从句中，不会出现WILL/WOULD。
★ We’ll have to cancel the show unless we sell more tickets at the last minute.
We’ll have to cancel the show if we do not sell more tickets.
We’ll have to cancel the show except if we sell more tickets at the last minute.
★ 除非我们在最后时刻卖出更多的票，否则将不得不取消演出。
★ You will feel cold unless you wear a coat.
You will feel cold if you don't wear a coat.
★ 除非你穿上外套，否则会觉得冷。
★ Unless it rains, we’ll go for a picnic by the river tomorrow.
We’ll go for a picnic by the river tomorrow if it doesn’t rain.
★ 除非下雨，否则我们明天会去河边野餐。
★ Unless you work hard, you will not pass the exam.
If you do not work hard, you will not pass the exam.
★ 除非你努力学习，否则就不能通过考试。
★ I'll arrive at 10am unless there is traffic.
I'll arrive at 10am if there isn't traffic.
★ 除非堵车，否则我上午10点能到。
◆ We don’t use UNLESS for impossible conditions, we use IF.
◆ UNLESS一般不用于非真实条件句。IF既可用于真实条件句，也可用于非真实条件句。
★ If the government had not raised food prices, there would not have been so many protests.
★ 要是政府没有提高食品价格，就不会有这么多的抗议活动。
◆ The verb that follows UNLESS has to be positive. It cannot be followed by a negative verb.
◆ UNLESS从句需是肯定句。
★ The government cannot operate effectively unless it is free from such interference.
★ 除非政府能排除这种干扰，否则将无法有效运转。
★ The gym is for members only. You can’t go unless you are a member. =except if
★ 健身房只对会员开放。除非你是会员，否则你进不去。
★ I’ll see you this afternoon unless I have to work. =except if
★ 除非我得工作，否则今天下午见。
★ We can walk to the restaurant, unless you would prefer to drive. =except if
★ 我们可以步行去餐厅，除非你更愿意开车去。
★ We cannot understand disease unless we understand the person who has the disease.
★ 除非我们了解患此疾病的人，否则我们无法了解此疾病。
◆ UNLESS can’t be used with a question.
◆ UNLESS不能用于疑问句中。
★ What will you do if you do not pass this final exam?
★ 如果没有通过这次期末考试，你会怎么做？
◆ In spoken English, we use UNLESS to introduce an extra thought or piece of information.
◆ 在英语口语中，UNLESS可用来引出一个额外的想法或信息。
★ He didn’t even know about the crash, unless he’s heard about it on the radio.
★ 他甚至不知道这起车祸，除非他从广播中听到了。
★ Look! Andy got a new car in front of his house – unless he’s got a visitor.
★快看！安迪家门口停了一辆新车 – 除非他家有访客。
Rewrite the following sentences use IF and UNLESS:
You must finish the job in time. Otherwise, you will be sacked.
If you do not finish the job in time, you will be sacked.
Unless you finish the job in time, you will be sacked.
除非你及时完成工作，否则你将被解雇。
You must not violate the rules. Otherwise, you will be in trouble.
If you violate the rules, you will be in trouble.
Unless you violate the rules, you will not be in trouble.
除非你违反规则，否则你不会有麻烦。
The boys must reach school in time. Otherwise, they will be punished.
If the boys do not reach school in time, they will be punished.
Unless the boys reach school in time, they will be punished.
除非男孩子们及时到达学校，否则将受到惩罚。
NOT UNLESS: = only if
★ “Shall I tell Andy what happened?” “Not unless he asks you.”
★ 我应该告诉安迪所发生的事吗？除非他问你，否则不用。
NOT UNLESS is a shorter way to say “You should not, unless she asks you”.
★ “Will you go with her?” “Not unless she wants me to.”
★ 你会和她一起去吗？除非她要我去，否则我不去。
★ “Will I have to pay?” “Not unless you want to.”
★ 我必须付钱吗？除非你想，否则不用。
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