后置定语一般是短语或句子来作定语,因为比较长放在被修饰词的后面.除了副词作定词永远放在后面外.the boy standing at the door.分词短语作后置定语the students who are reading in the classroom定语从句the people here 副词作定语the weather today同上主语从句:很简单就是一个句子来作主语.如(That he came late again) made his teacher angry.(What he said ) made us surprised.(Whether we can finish the work in time)is a problem.(When we will start ) is still unknown.It is unknown (when we will start)It is clear (that he is late)括号里的都是主语从句.