定语从句的分类
一:限制性定语从句 先行词与关系代词之间无逗号分隔,相当于一个后置定语,如: They are the boys who you like to play with. 二:非限制性定语从句 定语从句前有逗号分隔,主要起补充说明作用,如: Mr. Brown has a son, who joined the army 3 years ago.