The past perfect is used to talk about a past action. When we talk about a past action with the past perfect, we refer back to something that happened before.

Example : When I woke up, the film had already finished.
—> The film finished before I woke up.

How to form the past perfect :

– Affirmative form : Subject + had + past participle (eg. I had forgotten my phone.)
– Negative form : Subject + hadn’t + past participle (eg. I hadn’t forgotten my phone.)
– Question form : Had + subject + past participle (eg. Had I forgotten my phone ?)