Past perfect tense definition: It talks about an action that was completed before another action in the past. For example: We reached home last night at 9 pm. This is a time which is fixed in the past; last night. so at 9 pm last night we reached home there was no light. It means the light had gone before that 9 pm. So for such activities, we use past perfect tense. Past perfect tense Formula check out the Present perfect tense: 1. Positive formula/ structure. Subject + had (helping verb) + 3rd form of the verb + object/ complement. E.g. The plane had left before she arrived. We had eaten everything when he came home. She had broken the glasses before we became aware. Everything had been ruined when the police arrived. I had done my work. She had finished eating. 2. Negative formula/ structure. Subject + had + not + 3rd form of the verb + object/ complement. e.g. The plane had not left before she arrived. We had not eaten everything when he came home. She had not broken the glasses before we became aware. Everything had not been ruined when the police arrived. I had not done my work. She had not finished eating.