名词性从句在句子中起名词作用的句子叫名词性从句。名词性从句的功能相当于名词词组,它在复合句中能担任主语、宾语、表语、同位语、介词宾语等, 因此根据它在句中不同的语法功能,名词从句又可分为主语从句、宾语从句、表语从句和同位语从句。主语从句的用法一. 主语从句在复合句中作主语, 它可以位于句首, 但常见的主语从句多放在句末,句首则用形式主语it。1. That the earth is round is true. = It is true that the earth is round. 2. Whether he will come hasnt been decided. = It hasnt been decided whether he will come. 注意: 连词that, whether在从句中不担任句子成分,只起连接作用,不能省略 (注:if不可用来引导主语从句）二. 用it 作形式主语的结构(1) It is名词从句 It is a fact that
