The past perfect is used to explain that one action in the past happened before another action in the past. We form it by using had + past participle.
| Positive | Positive short form | Negative | Negative short form |
|---|---|---|---|
| I had eaten | I'd eaten | I had not eaten | I hadn't eaten |
| You had left | You'd left | You had not left | You hadn't left |
| She, he, it had worked | She, he, it'd worked | She, he, it had not worked | She, he, it hadn't worked |
| We had talked | We'd talked | We had not talked | We hadn't talked |
| They had thought | They'd thought | They had not thought | They hadn't thought |