主语主语是执行句子的行为或动作的主体，如“我写字”中的“我”，就是主语，它做出“写”这个动作。“写”则是谓语，而“字”是接受谓语“写”这个动作的对象，它因此被称为宾语，有的语法书也称它为“客体”或“受体”。
主语可以这些列词类或形式来担任：名词，代词，名词化了的动词，形容词，分词，副词或数词等，动词不定式或不定式短语，从句，某些固定词组的第二格。
作主语的词：名词，代词，名词化了的动词，形容词，分词，副词或数词等，动词不定式或不定式短语，从句，某些固定词组的第二格。
■1. 名词作主语
直到河里的鱼死了，村民们才意识到污染的危害。The villagers didn't realize how serious the pollution was until the fish in the river died.
S+ V t +O. 主系表结构 :S+V
倒装：Not until the fish in the river died did the villagers realize how serious the pollution was.
注意：倒装在主句，从句不倒装 /did 和not 提前，只剩动词原形
强调：It was not until the fish died in the river that the villagers realized how serious the pollution was.
如果强调的是主语或宾语且指人用who，其他一律用that。是that，而非其他/主句的顺序（（倒装不强调，强调就不倒装））
■2.代词作主语
人称代词（主格），名词性代词，指示代词，不定代词，such（----样的人、物），it（时间，天气，距离等）
at midnight /in the(泛指）middle of the night
It is 9 o'clock when I went home.
It was ten when I got home.一般句
It was at ten that I got home.强调句
I got home at ten.原形
■3.数词作主语
Ten out of 100 Americans are over /above /more than 65.
■4.动名词作主语
一般 / 完成时
v-ing: 主动/doing/having done
not doing:被动/being done/having done
注意：doing 无时间限定/与谓语同时出现/在谓语动词后发生having done发生在谓语之前
He still remembers being prized.
当逻辑主语为无生命的东西时
a.作主语时，通常表示一般性的无时间性的东西。而不定式表示某一种具体的动作。
Smoking is hobbit difficult to break.
b.主语和表语一致
Seeing is believing.
c.逻辑主语必须是所有格形式
Smoking kills.
d. it 作形式主语：It is no use/good-----
The old man's taking pity on the snake leads to his death.那个老头怜悯那条蛇，导致他的死亡。
■5.不定式作主语
To +动词原形
Not to do 解释：具有动词的性质，作宾语，状语/具有名词的性质，作主语/具有形容词性质，作定语/具有副词的性质，作状语。除谓语不可作之外，其他都可。
一般式：to do
进行时：to be doing
完成时：to have done
完成进行时：to have been doing
to do:表示动作发生在谓语之后，I want to go home.与谓语动词几乎同时发生
to be doing :表示与谓语动词同时发生
to have done:发生在谓语动词之前 Someone was considered to have done something.
to have been doing :动作从过去开始一直持续到谓语动词这个动作的发生
不定式表示一种确定的动作
To do morning exercises this morning is not good for your healthy.
注释：作主语在句首/it作主语构成（常用 v-ing，不常用只有 use，good）
It is +adj. +of sb.(人的属性）/for sb.（物的属性）to do
It is necessary to finish the design before National day. Tomorrow is National day.
it is +n.+for/of sb. to do
It is not good manners for Arabs to stand close talking to their friends.
It is a great honor for us to be invited to the party.
在感叹句中必须用it作形式主语：What a joy/ pleasure (it is) to read the book.
在问句中必须用形式主语：Is it possible to go to the moon by spaceship?
■6.名词化的形容词或过去分词
the poor / the disabled /the sick
■7.名词化的介词短语
From my home to school is three kilometers.
副词----不定式或动名词
What an excitement to find a shark when you’re swimming in the sea.
■8.句子作主语（从句一律为陈述句）
1)that引导的从句，无意义，不担当句子成分，不省略
A. It +v+ that从句
1.It +系动词+表语+that 从句
It is strange that he didn't come here yesterday.
当形容词为important necessary strange /that should +动词原形
It is strange that he should （表示吃惊）pass the exam.
2. It is +n +that 从句
What a pity it is that you didn't come to this party.
当名词为a pity/a shame /a surprise +should +v原形（表示竟然）
What a pity that she should be fail in exam.
3. It is +过去分词+that 从句
It is report that a car accident happened there.
从句s +be v-ed + inf.
He is said to be studying in the USA.
有人建议suggest/order/request + 从句 should +动词原形
4. It +动词原形seem/appear /turn out/+that
It seems that it will rain.
5. It strikes sb. that 从句 ，某人突然想
It occurs to sb. that-----
B.为强调从句意义，that从句常放在句首
That he will come here is of great help.
That you failed the exam will
--What made his father so angry?
--That he failed the exam. 或He fails the exam.
c.在问句中必须有形式主语
It is true that Bush will visit China again?
2) Whether /if是否不担当句子成分，也不省略
A.句首只用whether
Whether he will come to the meeting is unknown yet.
B.句末形式主语都可用 It ----whether/if
It is of no/little important whether/if it will rain today.
c.在有些句型中，从句不在前 It doesn't matter whether ----
It doesn't matter whether it is new/it will rain tomorrow.
3) 连接代词 who /whom/whose/what/which/担当从句成分，有意义，不省略
A. what +sb. + clause
What we will do next is not decided.
B. what+修饰词 意为什么样的……
What color you like is none of my business.
C. what ……人，……事，……物
What he said at the meeting surprised everyone present.
注意：what前是否有先行词/与that 之间的区别
That he said it at the meeting surprised everyone present.
What 与which 的区别
Which/what you want---若给定范围用which，没有用what。
What ---be that---强调句的一种（强调后者）
What I need most is that someone helps me.
There be +what clause
There was we call People's Republic of China in Chinese history.
What +比较级 what more /what worse
what引导从句作状语修饰全句的内容。在句首或句中，很少在句尾
Which +n (single)
Whose +n(只用此）
Whose father is a doctor is no sense.
It从句作形式主语（what……人或物时，不用it）
4）连接副词 when/whose/how/why担当句子成分，有意义，不省略
How the accident happened puzzled everyone.句尾用形式主语it
5) 引导主语从句
whoever/whosever/whatever/whichever/Anywhere/anything that /everyone that/whoever=anyone whom/anything that (泛指)/anything what (特指)
Whoever 指人从意义判断
Who 引导指事
Since the introduction of reform, China has made earth shaking changes.自从改革以来，中国发生了翻天覆地的变化。
英语省略主语的用法
■祈使句自然可省去主语，如：
Leave him in peace! 不要去打扰他!
■除祈使句外，还有其他省去主语的情况，如：
Don’t know. 我不知道。(省去主语I)
■There be结构中的there有时也可省去，如：
Appears to be a big crowd in the hall. 大厅里似乎有一大群人。
