When we talk about something that happened in the past we sometimes want to refer back to something that happened before that time. We can use the past perfect tense ( had + past participle ) to do this.
当我们谈论过去已经发生的某事，经常是指之前已经发生过的某事，我们可以用过去完成时态（had + 过去分词 ）来表示。
Look at these two sentences.
看一下这两句。• John left the house at 7:30 yesterday morning.
• Mary rang John’s doorbell at 8:15 yesterday.
Both actions happened in the past so we use the past simple tense. But look at how we can combine the sentences.
这两个动作都发生在过去所以我们用了一半过去时态，但是，看看我们如何把两个句子结合在一起。• Mary rang John’s doorbell at 8:15 yesterday but John had already left the house.
We use the past perfect (had left) because the action happened before another action in the past (Mary rang the doorbell.)
had left用过去完成时，是因为该动作在过去发生的另外一个动作Mary rang the doorbell.之前发生的。
Look at some more examples of the past perfect.
看看过去完成时的更多例子。• When Mrs Brown opened the washing machine she realised she had washed the cat.
• I got a letter from Jim last week. We’d been at school together but we’d lost touch with each other.
The past perfect is used because they were at school before he received the letter. It refers to an earlier past.
Look at these 2 sentences.
看下这两句。• James had cooked breakfast when we got up.
• James cooked breakfast when we got up.
In the first sentence, the past perfect tells us that James cooked breakfast before we got up. In the second sentence, first we got up and then James cooked breakfast.
Past perfect continuous
The past perfect can also be used in the continuous.
过去完成时也可以用于进行时。• I realised I had been working too hard so I decided to have a holiday.
• By the time Jane arrived we had been waiting for 3 hours.
The most common mistake with the past perfect is to overuse it or to use it simply because we are talking about a time in the distant past.
最常见的过度使用过去完成时的错误，就是仅仅是用它形容遥远的过去的时间。• The Romans had spoken Latin
Remember that we only use the past perfect when we want to refer to a past that is earlier than another time in the narrative.