专四语法常考高频考点高频考点1: 句子成分句子成分指的是组成句子的成分。
句子中必须具备的成分包括主语、谓语；可能有的成分包括宾语、补语、修饰语(定语、状语、同位语)。
近年专四考试中，主要考查某个词、短语或从句在句中充当的成分，同位语、补语、形式主语、形式宾语等是考查热点。
真题例证Xinchun returned from abroad a different man. The italicized part functions as a(n) in the sentence.A. appositiveB. objectC. adverbialD. complement【解析】本题考查句子成分分析。
a different man接在动词之后，但却是对主语Xinchun起着解释或描述作用的成分，因此为主语补足语。
因此选D。
高频考点2: 虚拟语气1. if条件句中的虚拟语气2. insist/ suggest/ propose/ advise/ recommend/ order/ command/ demand/ require/ request/ + that + (should)动词原形3. if only引导的感叹句if only从语义和用法上都相当于I wish，后面的谓语动词用一般过去时表示目前的愿望，用过去完成时表示过去的愿望，用would/could do表示对将来期望。
1) 表示与现在相反的愿望：wish/if only + 主语+ 动词过去式；2) 表示与过去相反的愿望：wish/if only + 主语+ had + 过去分词；would/could + have + 过去分词；3) 表示与将来相反的愿望：wish/if only + 主语+ would/could/might + 动词原形。
真题例证If there were no subjunctive mood, English much easier to learn.A. could have beenB. would beC. will beD. would have been【解析】本题表示与现在事实相反的假设，考查虚拟语气。
表示与现在事实相反，条件从句用一般过去时，主句使用should (would)+动词原形。
本题选B。
高频考点3: 情态动词1. 情态动词的一般用法情态动词在英文中主要用来表示说话人的看法、态度等。
英文中的情态动词主要有：can, could; may, might; must; ought; need; dare；另外shall, will, should, would在一定的场合也可用作情态动词。
表示对目前状况、目前正在进行的动作的猜测，结构如下：must/may/might be + 名词/介词短语/v.-ing/v.-ed/副词；当上述结构用于疑问式或否定式时，must常用can取代。
2. 情态动词与完成时的连用1) needn't have done表示过去做了某事，但事实上没有做的必要，意为"本不必要……";2) can't/couldn't have done表示推测某种动作不可能发生;3) may/might have done表示对过去事情的推测;4) must have done表示对过去事情的肯定推测，其疑问形式用can/could来表示，否定形式用can't/couldn't;5) should/would have done表示本应该做某事却没有做，用于对已发生的情况表示"责备"、"不满"。
真题例证Nancy's gone to work but her car's still there. She by bus.A. must have goneB. should have goneC. ought to have goneD. could have gone【解析】本题考查情态动词的用法。
must have done表示对过去事情的肯定推测，根据句意应选A。
高频考点4: 状语从句1. 让步状语从句连接词让步状语从句可由下列连词或结构引导：though/although (虽然), even if/even though (即使), however (尽管), whatever (不管), no matter (how, what, where, when) (不管[怎样、什么、哪里、何时]), whether (... or) (不管), granted that (即使), for all that (尽管如此), in spite of the fact that (尽管), regardless of the fact that (尽管)等。
此外，while引导让步状语从句时，只能放在句首，意义上相当于although。
2. 条件状语从句条件状语从句可由下列连词引导: if, unless, as long as/ so long as, on condition that, suppose/ supposing, provided/ providing that, granted/ granting (that), given (that), in the eve nt that等。
3. 原因状语从句原因状语从句可由下列连词引导: because, since, in that, now that, seeing that, considering that, in as much as, by reason that, for the reason that, on the ground that等。
4. 结果、目的状语从句1) 结果状语从句通常由以下连接词(组)引导: so... that..., such... that..., so that, that, consequently, to such a degree/an extent that, with the result that等。
2) 目的状语从句通常由以下连接词(组)引导：so that, in order that, that, in the hope that, for the purpose that, to the end that等。
5. 时间状语从句时间状语从句通常由以下连接词(组)引导: when, while, as, immediately, once, directly, instantly, as soon as, no sooner... than, scarcely/ hardly/ barely... when, every time, any time, next time, the moment, the minute, the instant, the day, the year, till, until。
真题例证He asked me to lend him some money, which I agreed to do, that he paid me back the following week.A. on occasionB. on purposeC. on conditionD. only if【解析】本题考查词组的含义和用法。
四个选项中只有C项on condition后面跟that从句，是正确答案，表示"在……条件下，如果，倘若"。
A项on occasion表示"间或，有时"；B项on purpose"故意"；D项only if"只要，只有"，用于句首时，后面主句的主谓语要倒装。
高频考点5: 名词性从句名词性从句多由连词that，whether/if, wh-疑问词或由what或wh-ever关系代词引导，根据表示法分类，名词性从句主要有三种，即that从句，wh-从句和whether、if引导的名词性从句。
真题例证Which of the following italicized parts is a subject clause (主语从句)?A. We are quite certain that we will get there in time.B. He has to face the fact that there will be no pay rise this year.C. She said that she had seen the man earlier that morning.D. It is sheer luck that the miners are still alive after ten days.【解析】本题考查句子结构。
D中的It是形式主语，that引导真实的主语从句。
本题选D。
高频考点6: 主谓一致处理主谓一致有如下三条原则：1) 语法一致，即：主语为单数形式，谓语动词也采用单数形式；主语为复数形式，谓语动词也采用复数形式(不包括复数形式单数概念的名词)。
2) 概念一致，即：谓语动词的单、复数形式要取决于主语所表达的概念，而不取决于表面的语法标志。
3) 就近原则，即：谓语动词的单、复数形式取决于最靠近它的主语。
真题例证Which of the following sentences is grammatically INCORRECT?A. Politics are the art or science of government.B. Ten miles seems like a long walk to me.C. Mumps is a kind of infectious disease.D. All the furniture has arrived undamaged.【解析】本题考查主谓一致。
politics作"政治学"讲时，谓语动词用单数，因此A项语法上错误。
ten miles看作整体，因此用单数；mumps"腮腺炎"虽以s结尾，却是不可数名词，谓语用单数；furniture 是不可数名词，因此也用单数。
高频考点7: 非谓语动词非谓语动词顾名思义，是指不作谓语的动词，主要包括动词不定式、动名词、现在分词、过去分词。
非谓语动词可作主语、宾语、状语、定语、补语等，专四考试中常考非谓语动词作状语、主语、宾语。