英語句子成分－主語講解 什么是主語？
主語相當(dāng)于句子的話題或主題，即要說明的人或物。主語一般位于句首，且不能省略。但在某些特定的句式里，如：疑問句倒裝句祈使句感嘆句等，句子主語也可以位于謂語動詞之后或省略。【想一想】哪些詞類或短語可以用作主語？（答：能用來做主語的有：名詞、代詞、數(shù)詞、動名詞或動名詞短語、動詞不定式或動詞不定式短語、主語從句等。）
1.名詞（或名詞詞組）
My pen is green. (單數(shù)可數(shù)名詞)
Jane is an American girl. (專有名詞)
2.代詞
I am a student. (主格人稱代詞)
Her pen is blue, and mine is red.（名詞性物主代詞）
These are my books. (指示代詞)
Who is not here today? (疑問代詞)
Nothing was wrong with his eyes. (不定代詞)
3.數(shù)詞
Two and one is three. (基數(shù)詞)
The second was a tall man. (序數(shù)詞)
4.動名詞
Eating too much is bad for your health. (動名詞)
Playing games is much better than staying at home. (動名詞短語)
5.形容詞
The rich are not always happy.(少數(shù)形容詞前邊加the 相當(dāng)于名詞)
6.動詞不定式
To see is to believe.(動詞不定式)
It will take you 2 hours to get to the station.(it作形式主語，動詞不定式短語作真正主語)
7.主語從句（僅作了解）
What the teacher said yesterday is important.
△幾個常見加the后可以名詞化的形容詞是：poor, rich, young, old，happy,blind, beautiful等。
△主語和謂語的順序有兩種：（1）自然順序，即主語在前，謂語在后；（2）倒裝語序，即謂語或謂語的一部分在前， 主語位于其后。例如：
Are you a student？
Do you like English songs?
What do you speak?
There is a bird in the tree. (there be 句型)
Here is your pen. (以副詞here/there開頭的句子習(xí)慣上主謂倒裝)
There stands a policeman.