介绍了英语语法中的复合句，包括主句和从句的概念，以及名词从句、形容词从句和副词从句的用法。
在英语语法中，复合句是由两个或以上的子句组成的句子。其中，一个子句是主句，其余子句是从句。复合句可以让我们在表达中更加丰富，也可以帮助我们更准确地表达复杂的思想。
主句和从句
复合句由主句和从句两部分组成。主句通常包含一个完整的意思，而从句则不能独立成句，需要依靠主句才能完整表达意思。从句在复合句中充当不同的角色，可以是名词从句、形容词从句或者副词从句。
名词从句
名词从句在复合句中充当名词的作用，可以作为主语、宾语、表语或者介词宾语等。例如：
- What he said is true. (名词从句作为主语)
- I don't know where she is. (名词从句作为宾语)
- Her dream is to become a doctor. (名词从句作为表语)
- I'm interested in what you are doing. (名词从句作为介词宾语)
形容词从句
形容词从句在复合句中充当形容词的作用，修饰一个名词或代词。例如：
- The book that I read yesterday was very interesting. (形容词从句修饰名词book)
- She is the girl who won the prize. (形容词从句修饰代词girl)
副词从句
副词从句在复合句中充当副词的作用，用来修饰动词、形容词、副词或整个句子。例如：
- He will come back when he finishes his work. (副词从句修饰动词come back)
- She is so beautiful that everyone likes her. (副词从句修饰形容词beautiful)
- He speaks English fluently because he has studied it for many years. (副词从句修饰整个句子)
复合句在英语中非常常见，掌握复合句的构成和用法对于提高英语表达能力非常有帮助。