学习任何一门科目都离不开对的知识点,尤其是同学们在学习英语时,更要总结各个语法知识点,这样也方便同学们日后的复习。下面小编为大家带来高三英语语法必背知识点，希望对您有所帮助!
高三英语语法必背知识点
虚拟语气在一些特殊词中的使用或含蓄条件句
1.wish后的宾语从句。
与现在愿望不一致，用主语十过去时，例如：
I wi。hIwere you.
与过去愿望不一致，用主语+had+过去分词，例如：Iwish I had visited the White House whenI was in the States与将来愿望不一致，用主语+would (could)+原形。
2.It's time句型：当lt's tine后用that从句时应该为主i吾+should+动词原形或主语十过去时，例如：It，s time thatyou went to school.或It's time that you should go to schooL
3- If only引起的感叹句相当于“How I wish+宾语从句”。
(l)If only he could come.他要能来就好了。
(2)If only I had known the answer.我要早知道答案就好了。
4.WOuld rather，as if(though)引导的从句也需使用虚拟语气，表示过去的情况用过去完成时，表示现在与将来的情况用过去时，例如：
(l)I'd rather you posted the letter right away.
(2)She loves the children as if they were hers.
5.含蓄虚拟条件句含蓄条件句是指句中没有明显的虚拟条件句，而是利用其他手段来暗示存在虚拟条件。但是这类隐含式虚拟条件句往往都可以转化为if引导的条件句。常用来表示含蓄虚拟条件的手段有：
(1)介词或介词短语。如but for，but that，without,in case of, under more favorable condition等。
(2)连词。如so that, unless, in case, supposing,lest, provided(倘若……)，for fear that(唯恐)，in orderthat, on condition that, if only(要是……就好了)等。
注意：lest, for fear that和in case引起的从句中谓语动词多用should+动词原形，但也可以不用虚拟语气，而用动词的陈述语气形式。例如：The foreign teacher spokeslowly in case we misunderstood him这位外籍教师说得很慢以免我们误解。
(3)通过上下文及内在含义，句中往往有but,otherwise, unfortunately等类似转折词。
without, but. but for, otherwise引起的短语或句子常暗含着含蓄条件。例如：
①Without you,1 would never know him
②But for your oooperation, we wouldn't have done it
③But that she was afraid, she would have said no. .
④i would be most glad to help you, butI am busy now.
⑤I would have come to the party yesterday, but ljwas working.
⑥I am busy now, otherwise l would do you the favor!
高三英语语法基础知识点
一、不定式做主语：
1、不定式做主语一般表示具体的某次动作。动名词doing表示习惯的，经常的动作。
e.g:Tofinishthebuildinginamonthisdifficult.
Todosuchthingsisfoolish.
Toseeistobelieve.(对等)
注:1).不定式作主语时,谓语用单数
2).当主语较长，谓语较短时，常用it做形式主语，而将不定式放到谓语的后面。
it做形式主语，不定式放在谓语动词之后常用于下列结构中：
(1)Itis/was+adj.+ofsb.todo…
(2)Itis+adj.+forsb.+todo…
Itiseasy/difficult/hard/foolish/unwise/right/wrong/unnecessary
(3)itis+a+名词+todo...
Itisapity/apleasure/apleasantthing/one’sduty/anhonor/ashame/acrime/noeasyjob…todo
Ittakes(sb.)sometime/courage/patience…todo…
Itrequirescourage/patience/hardwork…todo…
注意:probable和possible均可作表语，但possible可以用不定式作真实主语，而probable不能用不定式作真实主语。
Itisprobableforhimtocometothemeeting.(错)
Itispossibleforhimtocometothemeeting.
Itispossible/probablethathewillcometothemeeting.
高三英语语法重要知识点
用固定的情态动词表示的虚拟语气
1. should +动词原形(有时省略should)
(1)用在动词如advise, command, demand, desire, insist, order, propose, recommend, request, require, suggest, urge等后的宾语从句中。例如：
1)They requested that we (should) send a delegation to their country.
2)She urged that he write and accept the post.
(2)用在it is suggested, it is desired, it is required, it was ordered, it was proposed, it has been decided, it is necessary (essential, imperative, important, desirable) that等引出的主语从句中。例如：
1)It is desired that we (should) get everything ready by tonight.
2)It is necessary that the teacher (should) have a thorough knowledge of the subject he teaches.
(3)用在suggestion, motion, proposal, order, recommendation, plan, idea, requirement等引起的表语从句和同位语从句
例如：He put his coat over the child lest he should catch cold.
