1. (表示条件)如果 ,主句用将来时，if从句用现在时表示将来
He will come if you invite him.
如果你请他,他会来的。
2. (表示虚拟)假如,要是
1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
a. 同现在事实相反的假设。
句型 ： 条件从句 主句
一般过去时 should( would) +动词原形
If they were here, they would help you.
b. 表示于过去事实相反的假设。
句型： 条件从句 主句
过去完成时 should(would) have+ 过去分词
If she had worked harder, she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday, he would have prevented me from going.
If he had come yesterday, I should / would have told him about it.
含义：He did not come yesterday, so I did not tell him about it.
If he had not been ill and missed many classes, he would have made greater progress.
含义： He was ill and missed many lessons, so he did not make greater progress.
c. 表示对将来的假想
句型： 条件从句 主句
一般过去时 should+ 动词原形
were+ 不定式 would + 动词原形
should+ 动词原形
If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were o sutcceed, everything would be all right. 虚拟语气表示说话人的愿望、假设、猜测或建议，不是表示客观存在的事实，因此虚拟语气常用在含有非真实条件从句的主从复合句中。 虚拟语气在条件句中的用法：
虚拟条件句是用谓语动词的特殊形式来表示与现在、过去事实或将来事实相反的情况。虚拟条件句中所用的谓语动词的过去时、过去完成时、过去将来时等只表示不同的虚拟语气，与陈述语气句中的过去时、过去完成时等没有关系。具体情况如下：
1. 表示与现在事实相反的假设时，条件从句中的谓语动词用“过去式(be的过去式用were)”，而主句中的谓语动词用“would (should, could, might) + 动词原形”。例如：
If he had time, he would attend the meeting.
如果他有时间，他会参加这次会议。
If I were a bird, I could fly in the air.
如果我是一只小鸟，我就能在空中飞行。
2. 表示与过去的事实相反的假设时，条件从句的谓语动词用“had + 过去分词”，主句中的谓语动词用“would (should, could, might) + have + 过去分词”。例如：
If you had taken my advice, you wouldn’t have failed in the examination. 如果你接受我的建议，在这次考试中你就不会失败。
If you have worked hard, you wouldn’t have failed in the exam.
如果你早用功，你就不至于考试不及格了。
3. 表示与将来事实相反的假设时，条件从句的谓语动词用“过去式 / should + 动词原形 / were to + 动词原形”，主句中的谓语动词用“would (should, could, might) + 动词原形”。例如：
If it were to rain tomorrow, the meeting would be put off.
假如明天下雨，会议就会被推迟。
提示：⑴ 用虚拟语气表示条件的条件从句，可以放在主句前，也可放在主句后，但所表达意义的侧重点不同。主句在前时，强调“结果”；从句在前时，强调“条件”。
⑵ 在书面语中有时可省略条件从句中的if，但须将从句中的were, had, would或should放到从句中的主语之前。例如：
Were I in school again, I would work harder.
如果我能再上学，我就会更努力地学习。
Should there be a meeting tomorrow, I would come.
如果明天有会议，我会来的。
Had you arrived at the station ten minutes earlier yesterday, you could have caught the train.
如果你昨天早十分钟到火车站，你就赶上火车了。
⑶ 可用介词短语代替条件从句。例如：
If there weren’t air, there would be no living things.
= Without air, there would be no living things.
如果没有空气，就会没有生命。
【巩固精练】用所给动词的正确形式填空。
1. If it rained, they ___________ (stay) at home.
2. We would be very much pleased if you ___________ (come).
3. What a pity! I haven’t got my car. If I had, I _______ (take) you to the airport.
4. We would answer the questions if we ___________ (can).
5. If I were you, I __________ (take) a long walk before going to bed.
Keys：1. would stay2. came3. would take4. could5. would take
高考虚拟语气的归纳
间接引语中的条件句
高中英语语法：虚拟语气
虚拟语气常见错误
虚拟语气的用法
http://www.ryedu.net/syy条件句有真实条件句和非真实(虚拟)条件句两种。真实条件句所表示的假设是有可能发生的，而非真实条件句则通常表示一种假想，与事实相反或不大可能会发生：
If I have time, I will go with them. 假若我有时间，我就同他们去。(陈述语气)
If I were you, I would go with them. 假若我是你，我就同他们去。(虚拟语气)
虚拟条件句的三种基本类型
一、与现在事实相反
若与现在事实相反，条件从句的谓语用过去式(be通常用were)，主句谓语用“should
(would, could, might)+动词原形”：
If you took a taxi，you’d get there quicker. 如果你坐出租车去，你可以快一点到那里。(但你不坐)
If I knew her number I could ring her up. 要是我知道她的电话号码，我就可以给她打电话了。(可惜我不知道)
二、与过去事实相反
若与过去事实相反，条件从句的谓语用过去完成时(had+过去分词)，主句谓语用“should (would, could, might)+have+过去分词”：
If I’d left sooner，I’d have been on time. 要是我早点动身，我就准时到了。(但我动身太
迟了)
If we had found him earlier we could have saved his life. 要是我们当时早点找到他的话，我们就可以救活他。(可惜我们找到他太晚了)
三、与将来事实相反
若与将来事实相反，条件从句的谓语用过去式(be通常用were)，主句谓语用“should
(would, could, might)+动词原形”：
If he went，would you go too? 如果他去，你也去吗?(大概他不会去)
If I asked him，I’m sure he’d help us. 如果我向他提出要求，肯定他会帮助我们。(不过我不打算这样做)
/zxyy/200906/13177.html注：几点特别说明
① 主句谓语中的should主要用于第一人称后。would, might, could的大致区别是：would表示结果，might表示可能性，could表示能力、允许或可能性。比较：
If you tried again you would succeed. 要是你再试一试，你就会成功的。(would表结果)
If you tried again you might succeed. 要是你再试一试，你可能会成功的。(might表可能) If you tried again you could succeed. 要是你再试一试，你就能成功了。(could表能力)
② 条件从句的谓语动词为be时，不管其主语为单数还是复数通常都用were，但在口语或非正式文体中的单数第一人称和第三人称后，也可用was，不过在 If I were you这样的表达中，通常还是以用were为宜。
③ 有时条件从句用would表示愿意：
If he would live on with me, I would be his better half. 要是他还愿意跟我过，我仍会做他
的妻子。
④ 对于与将来事实相反的情形，请注意以下几点：一是这里说的与将来事实相反，实为对将来情况的推测；二是此用法中的条件从句谓语除用过去式外，有时也用“should+动词原形”(表示可能性极小，常译为“万一”)或“were to+动词原形”(表示与将来事实相反的假设)；三是当条件从句使用“should+动词原形”这样的谓语时，主句谓语除可用“should (would, could, might)+动词原形”这样的虚拟语气外，也可用陈述语气或祈使语气：
If it should rain tomorrow, don’t expect me. 万一明天下雨，就不要等我了。
I should see him, I’ll tell him. 万一我见到他，我就告诉他。
1. (表示条件)如果 ,主句用将来时，if从句用现在时表示将来
He will come if you invite him.
如果你请他,他会来的。
2. (表示虚拟)假如,要是
1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。
a. 同现在事实相反的假设。
句型 ： 条件从句 主句
一般过去时 should( would) +动词原形
If they were here, they would help you.
b. 表示于过去事实相反的假设。
句型： 条件从句 主句
过去完成时 should(would) have+ 过去分词
If she had worked harder, she would have succeeded.
The rice would not have been burnt if you had been more careful.
If my lawyer had been here last Saturday, he would have prevented me from going.
If he had come yesterday, I should / would have told him about it.
含义：He did not come yesterday, so I did not tell him about it.
If he had not been ill and missed many classes, he would have made greater progress.
含义： He was ill and missed many lessons, so he did not make greater progress.
c. 表示对将来的假想
句型： 条件从句 主句
一般过去时 should+ 动词原形
were+ 不定式 would + 动词原形
should+ 动词原形
If you succeeded, everything would be all right.
If you should succeed, everything would be all right.
If you were o sutcceed, everything would be all right. 虚拟语气表示说话人的愿望、假设、猜测或建议，不是表示客观存在的事实，因此虚拟语气常用在含有非真实条件从句的主从复合句中。 虚拟语气在条件句中的用法：
虚拟条件句是用谓语动词的特殊形式来表示与现在、过去事实或将来事实相反的情况。虚拟条件句中所用的谓语动词的过去时、过去完成时、过去将来时等只表示不同的虚拟语气，与陈述语气句中的过去时、过去完成时等没有关系。具体情况如下：
1. 表示与现在事实相反的假设时，条件从句中的谓语动词用“过去式(be的过去式用were)”，而主句中的谓语动词用“would (should, could, might) + 动词原形”。例如：
If he had time, he would attend the meeting.
如果他有时间，他会参加这次会议。
If I were a bird, I could fly in the air.
如果我是一只小鸟，我就能在空中飞行。
2. 表示与过去的事实相反的假设时，条件从句的谓语动词用“had + 过去分词”，主句中的谓语动词用“would (should, could, might) + have + 过去分词”。例如：
If you had taken my advice, you wouldn’t have failed in the examination. 如果你接受我的建议，在这次考试中你就不会失败。
If you have worked hard, you wouldn’t have failed in the exam.
如果你早用功，你就不至于考试不及格了。
3. 表示与将来事实相反的假设时，条件从句的谓语动词用“过去式 / should + 动词原形 / were to + 动词原形”，主句中的谓语动词用“would (should, could, might) + 动词原形”。例如：
If it were to rain tomorrow, the meeting would be put off.
假如明天下雨，会议就会被推迟。
提示：⑴ 用虚拟语气表示条件的条件从句，可以放在主句前，也可放在主句后，但所表达意义的侧重点不同。主句在前时，强调“结果”；从句在前时，强调“条件”。
⑵ 在书面语中有时可省略条件从句中的if，但须将从句中的were, had, would或should放到从句中的主语之前。例如：
Were I in school again, I would work harder.
如果我能再上学，我就会更努力地学习。
Should there be a meeting tomorrow, I would come.
如果明天有会议，我会来的。
Had you arrived at the station ten minutes earlier yesterday, you could have caught the train.
如果你昨天早十分钟到火车站，你就赶上火车了。
⑶ 可用介词短语代替条件从句。例如：
If there weren’t air, there would be no living things.
= Without air, there would be no living things.
如果没有空气，就会没有生命。
【巩固精练】用所给动词的正确形式填空。
1. If it rained, they ___________ (stay) at home.
2. We would be very much pleased if you ___________ (come).
3. What a pity! I haven’t got my car. If I had, I _______ (take) you to the airport.
4. We would answer the questions if we ___________ (can).
5. If I were you, I __________ (take) a long walk before going to bed.
Keys：1. would stay2. came3. would take4. could5. would take
高考虚拟语气的归纳
间接引语中的条件句
高中英语语法：虚拟语气
虚拟语气常见错误
虚拟语气的用法
http://www.ryedu.net/syy条件句有真实条件句和非真实(虚拟)条件句两种。真实条件句所表示的假设是有可能发生的，而非真实条件句则通常表示一种假想，与事实相反或不大可能会发生：
If I have time, I will go with them. 假若我有时间，我就同他们去。(陈述语气)
If I were you, I would go with them. 假若我是你，我就同他们去。(虚拟语气)
虚拟条件句的三种基本类型
一、与现在事实相反
若与现在事实相反，条件从句的谓语用过去式(be通常用were)，主句谓语用“should
(would, could, might)+动词原形”：
If you took a taxi，you’d get there quicker. 如果你坐出租车去，你可以快一点到那里。(但你不坐)
If I knew her number I could ring her up. 要是我知道她的电话号码，我就可以给她打电话了。(可惜我不知道)
二、与过去事实相反
若与过去事实相反，条件从句的谓语用过去完成时(had+过去分词)，主句谓语用“should (would, could, might)+have+过去分词”：
If I’d left sooner，I’d have been on time. 要是我早点动身，我就准时到了。(但我动身太
迟了)
If we had found him earlier we could have saved his life. 要是我们当时早点找到他的话，我们就可以救活他。(可惜我们找到他太晚了)
三、与将来事实相反
若与将来事实相反，条件从句的谓语用过去式(be通常用were)，主句谓语用“should
(would, could, might)+动词原形”：
If he went，would you go too? 如果他去，你也去吗?(大概他不会去)
If I asked him，I’m sure he’d help us. 如果我向他提出要求，肯定他会帮助我们。(不过我不打算这样做)
/zxyy/200906/13177.html注：几点特别说明
① 主句谓语中的should主要用于第一人称后。would, might, could的大致区别是：would表示结果，might表示可能性，could表示能力、允许或可能性。比较：
If you tried again you would succeed. 要是你再试一试，你就会成功的。(would表结果)
If you tried again you might succeed. 要是你再试一试，你可能会成功的。(might表可能) If you tried again you could succeed. 要是你再试一试，你就能成功了。(could表能力)
② 条件从句的谓语动词为be时，不管其主语为单数还是复数通常都用were，但在口语或非正式文体中的单数第一人称和第三人称后，也可用was，不过在 If I were you这样的表达中，通常还是以用were为宜。
③ 有时条件从句用would表示愿意：
If he would live on with me, I would be his better half. 要是他还愿意跟我过，我仍会做他
的妻子。
④ 对于与将来事实相反的情形，请注意以下几点：一是这里说的与将来事实相反，实为对将来情况的推测；二是此用法中的条件从句谓语除用过去式外，有时也用“should+动词原形”(表示可能性极小，常译为“万一”)或“were to+动词原形”(表示与将来事实相反的假设)；三是当条件从句使用“should+动词原形”这样的谓语时，主句谓语除可用“should (would, could, might)+动词原形”这样的虚拟语气外，也可用陈述语气或祈使语气：
If it should rain tomorrow, don’t expect me. 万一明天下雨，就不要等我了。
I should see him, I’ll tell him. 万一我见到他，我就告诉他。