一、句子成分

(一)句子成分的定義：構成句子的各個部分叫做句子成分。句子成分有主要成分和次要成分;主要成分有主語和謂語;次要成分有表語、賓語、定語、狀語、補足語和同位語。

(二)主語：主語是一個句子所敘述的主體，一般位于句首。但在there be結構、疑問句(當主語不疑問詞時)和倒裝句中，主語位于謂語、助動詞或情態動詞后面。主語可由名詞、代詞、數詞、不定式、動名詞、名詞化的形容詞和主語從句等表示。例如：

During the 1990s, American country music has become more and more popular.(名詞)

We often speak English in class.(代詞)

One-third of the students in this class are girls.(數詞)

To swim in the river is a great pleasure.(不定式)

Smoking does harm to the health.(動名詞)

The rich should help the poor.(名詞化的形容詞)

When we are going to have an English test has not been decided.(主語從句)

It is necessary to master a foreign language.(it作形式主語，真正的主語為后面的不定式)

(三)謂語：謂語說明主語所做的動作或具有的特征和狀態。動詞在句中作謂語，一般放在主語之后。謂語的構成如下：

1、簡單謂語：由一個動詞或動詞短語構成。如：He practices running every morning.

2、復合謂語：(1)由情態動詞或其他助動詞加動詞原形構成。如：You may keep the book for two weeks. He has caught a bad cold. (2)由系動詞加表語構成。如：We are students.

(四)表語：表語用以說明主語的身份、特征和狀態，它一般位于系動詞(如be, become, get, look, grow, turn, seem等)之后。表語一般由名詞、代詞、形容詞、分詞、數詞、不定式、動名詞、介詞短語、副詞及表語從句表示。例如：

Our teacher of English is an American.(名詞)

Is it yours?(代詞)

The weather has turned cold.(形容詞)

The speech is exciting.(分詞)

Three times seven is twenty one?(數詞)

His job is to teach English.(不定式)

His hobby(愛好)is playing football.(動名詞)

The machine must be out of order.(介詞短語)

Time is up. The class is over.(副詞)

The truth is that he has never been abroad.(表語從句)