表示在过去某一时刻或动作之前完成了的动作,即句子中的动作发生在“过去的过去”。可以用by,before等介词短语或一个时间状语从句来表示。比如:lily had just left when we arrived。
表示从过去的某一时刻开始,一直延续到过去另一时间的动作或状态,常和for, since构成的时间状语连用。比如:he had lived in the house for five years .
在含有定语从句的主从复合句中,如果叙述的是过去发生的事情,先发生的动作常用过去完成时。比如:i had returned the english book that i had borrowed from the library.
过去完成时还可用在hardlywhen, no soonerthan, it was the first (second, etc) time (that)等固定句型中。在这类句型中,要注意,有时会用到倒装语句。it was the second time that she had been late.
平时要多做时态类型的练习题,培养自己的语感。