1: A finished action before a second point in the past.
We usually use the past perfect to make it clear which action happened first. Maybe we are already talking about something in the past and we want to mention something else that is further back in time. This is often used to explain or give a reason for something in the past.
If it's clear which action happened first (if we use the words 'before' or 'after', for example), the past perfect is optional.
2: Something that started in the past and continued up to another action or time in the past. The past perfect tells us 'how long', just like the present perfect, but this time the action continues up to a point in the past rather than the present. Usually we use 'for + time'. We can also use the past perfect continuous here, so we most often use the past perfect simple with stative verbs.
3: To talk about unreal or imaginary things in the past. In the same way that we use the past simple to talk about unreal or imaginary things in the present, we use the past perfect (one step back in time) to talk about unreal things in the past. This is common in the third conditional and after 'wish'.
We don't use the past perfect a lot in English, but it is useful, and it sounds very good if you can use it correctly. Also, it's really easy to make - just the past simple of 'have' and the past participle.
The positive - make it with 'had' + the past participle (usually made by adding 'ed' to the infinitive, but a few verbs have irregular past participles ):
(Also, here's some help if you are not sure how to pronounce '-ed' at the end of a verb).
The short form for 'had' is 'd.
(Be careful not to confuse it with 'would'. Would is followed by the infinitive - 'I'd go', whereas had is followed by the past participle - 'I'd gone').
For the negative just add 'not':
And to make a 'yes / no' question put 'had' before the subject:
For 'wh' questions put the question word at the beginning:
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