为，即“过去的过去”。2. 时间状语：before, by the end of last year(term, month),etc.3. 基本结构：had + done.否定形式：had + not + done.一般疑问句：had放于句首。4. 用法1) 在told, said, knew, heard, thought等动词后的宾语从句种。例如：She said (that)she had never been to Paris. 她告诉我她曾去过巴黎。2) 在过去不同时间发生的两个动作中，发生在先，用过去完成时;发生在后，用一般过去时。例如：When the police arrived, the thieves had run away. 警察到达时，小偷们早就跑了。3) 表示意向的动词，如hope, wish, expect, think, intend, mean, suppose等，用过去完成时表示"原本…，未能…"。例如：We had hoped that you would come, but you didn't. 那时我们希望你能来，但是你没有来。注意： had hardly… when... 刚......就......。例如：I had hardly opened the door when I he hit me. 我刚打开门，他就打了我。had no sooner…than 刚…… 就……。例如：He had no sooner bought the car than he sold it. 他刚买了这辆车，转眼又卖了。