If it does not rain tomorrow,I will go to her home.为什么用助动词

If it does not rain tomorrow,I will go to her home.为什么用助动词
If it does not rain tomorrow,I will go to her home.为什么用助动词

If it does not rain tomorrow,I will go to her home.为什么用助动词
用doesn't rain,rain是动词,不可以和助动词is连起来用 rain本身就是动词,否定形式应该加助动词do,即doesn't rain,而is是be动词,后面应该接名词

因为if表“如果”，引导从句要注意主将从现，所以要用does
望采纳~

助动词用法：
助动词一般没有词意，不能单独作谓语动词。其作用在于帮助构成各种时态、语态、否定、疑问等。
1、助动词be（am, is, are, was, were, being, been）的用法
（1） be后跟现在分词构成进行时态。
Who is playing the violin?谁在拉小提琴？
She was reading a book...

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助动词用法：
助动词一般没有词意，不能单独作谓语动词。其作用在于帮助构成各种时态、语态、否定、疑问等。
1、助动词be（am, is, are, was, were, being, been）的用法
（1） be后跟现在分词构成进行时态。
Who is playing the violin?谁在拉小提琴？
She was reading a book then.那时她正在读书。
（2）be后跟过去分词构成被动语态。
He was asked to do the work.有人要他干这件工作。
You are invited to attend the meetintg.有人邀请你参加会议。
（3）be 后跟不定式作谓语，有如下几种情况：
①表示计划、安排将要发生的事。
Who are we to meet?我们要见谁呀？
I'm to have supper with John this afternoon.今天下午我要与约翰一起吃晚饭。
②表示指示、命令，否定式表禁止。
You are to see the headmaster today.今天你必须去见校长。
You are not to enter the room without permission.未经允许你不能进入房间。
③表示义务、责任等，同should。
You are to be back before 5.你得在5点钟以前回来。
What is to be done?该干什么。
④表示可能性，与情态动词may, can同义。
Such books are to be found in any library.这种书任何图书馆都有。
Not a sound was to be heard.一点声响也没有。
⑤表示后来发生的事，可以用来表示命运或注定
They say good-bye, little knowing that they were never to meet again.他们告别了，没想到再也不能相见了。
He was to regret the decision.他有一天会后悔做出这一决定的。
⑥用于习语
Where am I to go? 我该向何处去？
What am I to do? 我该怎么办？
2、助动词have(has, had, having)的用法
（1）助动词have可以构成完成时或完成进行时
He has been a doctor for 10 years.他当医生十年了。
This is the place I have been longing to visit.这就是我一直渴望参观的地方。
（2）和不定式构成谓语，表示客观上不得不做的事情。
We've missed the train. We'll have to wait for another one.我们己经误了火车，我们只能等下一列。
-Do we have to start work?我们得立刻工作吗？
-No. We don't have to.不，不必了。
3、do(does, did) 的用法
（1）构成疑问句或否定句
How did you know about it?你是怎样知道这件事的。
He does not smoke. 他不抽烟。
（2）加强语气。
He did tell that.他的确告诉了此事。
Do come and see us.一定来看我们。
（3）代替前面刚出现的动词，避免重复。
-You like popular music, don't you?你喜欢流行音乐，是吧？
-Yes , I do.是的，我喜欢。
He speaks French as fluently as she does.他讲法语和她讲的一样流利。
（4）用于倒装句中。
Never did he pay attention to my words.他从不注意我的话。
Only then did I understand the importance of English.只是那时，我才了解到英语的重要性。
（5）构成否定的祈使句。
Don't be so careless.不要那么粗心。
Do not hesitate to come for help.只管来求助。
4、shall(should)和will(would) 的用法
（1）shall(should)用于第一人称的将来时中，单纯表示来
I shall think it over.我要好好考虑一下。
When shall I see you again?我何时再见到你？
I rang up to tell her that I should leave for London. 我打电话告诉她我要去伦敦。
（2）will用于第二、第三人称的将来时态中，在现代英语中可以用于所有人称
He will be 30 next month. 他下月将是30岁。
You will have an English test tomorrow.明天你有英语小测验。
He wanted to know when you would finish the writing.他想知道你何时完成写作。

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