Past perfect

Situation: Jack left his apartment at 2:00. Ann arrived at his apartment at 2:15 and knocked on the door.
(a) When Ann arrived, Jack wasn’t there. He had left.
The Past Perfect is used when the speaker is talking about two different events at two different time in the past; one event ends before the second event happens.
In (a): There are two events, and both happened in the past: Jack left his apartment. Ann arrived at the apartment. To show the time relationship between the two events, we use the past perfect (had left) to say that the first event (Jack leaving his apartment) was completed before the second event  (Ann arriving at this apartment) occurred.
(b) Jack had left his apartment when Ann arrived.
Form: had + past participle
(c) He’d left. I’d left. They’d left etc.
Contraction: They/We/I/Yoy/He/She/It +’d
Compare The Present And The Past Perfect
(d) I am not hungry now. I have already eaten
The Present Perfect expresses an activity that occurred before now, at an unspecified time in the past, as in (d)
(e) I was not hungry at 1:00 P.M. I had already eaten
The Past Perfect expresses an activity that occurred before another time in the past.
In (e): I ate at noon. I was not hungry at 1:00 P.M, because I had already eaten before 1:00 P.M
Compare The Past Progressive And The Past Perfect
(f) I was eating when bob came
The Past Progressive expresses an activity that was in progress at a particular time in the past.
In (f): I began eat at noon. Bob came at 12:10. My meal was in progress when Bob came.
(g) I had eaten when Bob came
The Past Perfect expresses an activity that completed before a particular time in the past.
In (g): I finished eating at noon. Bob came at 1:00 P.M. my meal was completed before Bob came.

English Grammar On Android - Click Here