）过去完成时由“had+过去分词” 构成，过去完成时的动作表示过去某一时刻或某一动作之前完成的动作状态。句中常用by, before, until, when等词引导的时间状语。例如：
By the end of last year we had built five new houses.
I had learnt 5000 words before I entered the university.
2）过去完成时的动词还可表示过去某一时刻之前发生的动作或状态持续到过去某个时间或持续下去。例如：
Before he slept, he had worked for 12 hours.
8）过去将来时的用法
过去将来时表示从过去的某时间看将要发生的动作或状态。过去将来时由“should或would+动词原形”构成。第一人称用should,其他人称用would.例如：
They were sure that they would succeed.
9）现在完成进行时的用法
现在完成进行时由“have (has)+been+现在分词”构成，表示现在以前一直在进行的动作。有些词，如work, study, live, teach等用现在完成进行时与用现在完成时意思差不多。例如：
I have worked here for three years.
I have been working here for three years.
但多数动词在这两种时态中表示不同意思。例如：
I have written a letter（已写完）
I have been writing a letter（还在写）
注意：表示短暂动作的动词，如finish, marry, get up, come go等不能用这种时态。
