The past perfect is used to express something that happened before another point in time. It is often used to provide context, or an explanation for a specific action or result.
This tense is often used with the following time expressions:
... before
already
once, twice, three times, etc.
... by the time
Basic Construction
Positive
Subject + had + past participle + object(s) + time Expression
She had already eaten by the time the children came home.
Negative
Subject + had not (hadn't) + past participle + object(s) + time Expression
They hadn't finished their homework before the teacher asked them to hand it in.
Question
(Question Word) + had + subject + past participle + object(s) + time Expression
Where had you gone before the class began?
