所谓特指指的是限制性定语从句。补充说明指的是非限制性定语从句。that不能引导非限制性定语从句。 独一无二的东西只能用非限制性定语从句修饰,起补充说明作用。 She had to look after her husband, who was ill. 她得照顾她丈夫,她丈夫生病了。 本句只能用非限制性定语从句,起补充说明作用,因为根据相关婚姻法是一夫一妻制。(如果是多夫制则除外,可以用限制性定语从句) 本句如果用限制性定语从句。则是特指的那个 She had to look after her husband that(who) was ill. 她得照顾她的那个生病的丈夫。(言外之意,她有n个丈夫,其他不生病的丈夫不需要照顾) 明白区别了吗?追问