.句子成分（一）句子成分的定义：构成句子的各个部分叫做句子成分。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（当主语不是疑问词时）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
