主语从句,即在复合句中充当主语成分的句子,例如"That he finished writing the composition in such a short time surprised us all",他在很短的时间内写完作文让我们都很惊讶,此复合句主要描述的是某事让我们惊讶,某事就是该复合句的主语,因此“That he finished writing the composition in such a short time”便是该复合句的主语从句。
引导主语从句的连词主要有:
从属连词:that whether
连接代词:whom whose who whoever what whatever which whichever
连接副词:why when whenever where wherever how however