一、句子成分( 一) 句子成分有主要成分和次要成分; 主要成分有主语和谓语; 次要成分有表语、宾语、定语、状语、补足语和同位语。( 二) 主语：主语是一个句子所叙述的主体，一般位于句首。但在there be结构、疑问句( 当主语不疑问词时) 和倒装句中， 主语位于谓语、 助动词或情态动词后面。主语可由名词、代词、数词、不定式、动名词、名词化的形容词和主语从句等表示。例如：During the 1990s, American country music has become more and more popular.(名词 )We often speak English in class.(代词 ) One-third of the students in this class are girls.(数词 ) To swim in the river is a great pleasure.(不定式 )Smoking does harm to the health.(动名词 ) The rich should help the poor.(名词化的形容词) When we are going to have an English test has not been decided.(主语从句 )It is necessary to master a foreign language.(it作形式主语，真正的主语为后面的不定式 ) ( 三) 谓语： 谓语说明主语所做的动作或具有的特征和状态。动词在句中作谓语，一般放在主语之后。谓语的构成如下：1、简单谓语：由一个动词或动词短语构成。如：He practices running every morning.2、复合谓语： (1) 由情态动词或其他助动词加动词原形构成。如：You may keep the book for two weeks. He has caught a bad cold. (2) 由系动词加表语构成。如：We are students. ( 四) 表语： 表语用以说明主语的身份、特征和状态， 它一般位于系动词(如 be, become, get, look, grow, turn, seem等) 之后。表语一般由名词、代词、形容词、分词、数词、不定式、动名词、介词短语、副词及表语从句表示。例如：Our teacher of English is an American.(名词 )Is it yours?(代词 ) The weather has turned cold.(形容词 ) The speech is exciting.(分词 )Three times seven is twenty one?(数词 ) His job is to teach English.(不定式 ) His hobby(爱好 )is playing football.(动名词 ) The machine must be out of order.(介词短语 ) Time is up. The class is over.(副词 ) The truth is that he has never been abroad.(表语从句 ) ( 五) 宾语：宾语...
