if after until before 是用什么时态 初二英语

if after until before 是用什么时态 初二英语

可以参考《结束蹦单词时代：外教教你用连词》，中国书籍出版社：

IF，第62-63页

1. If I feel bored, (then) I read a book.
2. I drink some coffee if I feel tired.
3. If we go to England, (then) we will come and visit you.
4. I will see you tomorrow if I get the time.
5. If it rained, (then) I would bring an umbrella.
6. I would invite all my friends if I had a party.
7. If I were a horse, (then) I would gallop into the wild.
8. I would wear beautiful garments if I were a queen.
9. If I had saved him, (then) he would have lived.
10. I could have got on the train if I had arrived earlier.

if 这个连词虽然容易记住，但是因为可以用在条件从句和虚拟语气中，所以我们对其语法形式的运用应当极其谨慎。（1）第1、2句话用第一种条件从句。这种条件从句用来表示普遍真理、事实或习惯。if 前后都用一般现在时。（2）第3、4句话用第二种条件从句。这种条件从句用来表示未来中的可能性，即如果第一种情况发生的话，那么第二种情况很可能也会发生。if 从句中用一般现在时，主句中用情态动词 will。（3）第5、6、7、8句话用第三种条件从句。这种条件从句用来表示假想的情况和相应的行为（5、6）和不太可能发生的虚拟语气，与现在情况相反（7、8）。在 if引导的状语从句中，be 一律用 were，其他动词用相应的过去式。主句中用 will 的过去式 would 或 can 的过去式 could。（4）第9、10句话用第四种条件从句。这种条件从句用来表示根本不可能发生的虚拟语气，与过去事实相反。if 从句中用过去完成时，主句中用 would/ could/ may/ might ＋现在完成时。if 在句首的时候，从句后放逗号，并可以用连词 then 来表示“那么……就……”。if 在主句后面的时候，不能放逗号也不能用连词then。

UNTIL，第80-81页

1. Please wait for me till I come back.
2. Keep stirring the tea until the sugar has dissolved.
3. My computer had been working fine up till last night.
4. We will be staying here up until the day after tomorrow.
5. I was on the phone to my friend up to 1 o’clock in the morning.
6. He works from Monday through till Friday.
7. We talked through to the end of the night.

以上连词表示“直到”或“直到……为止”。till、until 放在主句后面，其后加从句，或和时间相关的宾语。up till、up until、up to、through till、through to 放在主句后面，其后加和时间相关的宾语。through till、through to 既可以被理解为“直到、直到……为止”又可以被理解为“一直到、一直到……为止”。这些连词既是口语又是书面语。

1. We are not having the meeting till next week.
2. He did not believe that I was maltreated till I showed him my bruises.
3. They had not returned till the sun had set.
4. I will not let you pass till you tell me what’s going on.
5. They are not sleeping until you read them a bedtime story.
6. She did not leave until midnight.
7. I had not rung the police until I was sure that the place was safe.
8. You may not see me until after graduation.
9. The performance is not until 3.00 this afternoon.
10. A: Don’t you have school?
B: Not until Monday.
11. A: Give me back my book!
B: Not until you apologize!

not...till、not...until 表示“直到……才”，和中文句法正好相反。not 前面可以放助动词 be/ do/ have 或情态动词，till、until 后面可以加宾语或从句。not until 表示“直到”或“直到……才”，并可以用在【主语＋be＋not until＋宾语】这样的句法中（宾语指时间），也可以用来回答或答复，not until 放在句子的开头，其后加宾语或从句。这些连词既是口语又是书面语。

BEFORE，第130-131页

1. Before dinner, I usually wash my hands.
2. Before sleeping, she always reads a book.
3. He often listens to music before he goes to school.
4. We got up in the morning to prepare our bags, and before leaving for our journey, we had a big brunch.
5. You can go out with your friends tonight, but before you go out, you must finish your homework.
6. Before, he was a beggar on the streets, but now he is a carpenter.
7. There was danger before, but now it is safe.
8. I have never been to New Zealand before.

第1到第5句中的 before 是介词或连词，表示“之前”、“在……之前”或“在……以前”。第6到第8句中的 before 是副词，表示“以前”。 before 表示“之前、在……之前”的时候，就放在句子的开头、两个分句之间，或 and/ but 后面，其后放名词、动名词，或从句。before 表示“以前”的时候，就放在句子的开头，其后放逗号，再放从句；也可以放在前句的句尾，或整句的句尾。

AFTER，第139-141页

1. After lunch, I usually drink a cup of coffee.
2. After several hours, our train finally arrived.
3. After exercising, he always takes a shower.
4. We occasionally go window-shopping after we have finished school.
5. I studied for five years, and then after my studies I looked for a job.
6. The children lived with their grandparents when they were little, but after they grew older, they moved back in with their parents.

after 是介词也是连词，表示“之后”、“以后”、“在…… 之后”、“在……以后”或“过……以后”。after 放在句子的开头、两个分句之间，或 and (then)/ but (then) 后面，其后放名词、动名词，或从句。

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