| Aspect | Past Perfect Simple | Past Perfect Continuous |
|---|---|---|
| Structure | Subject + had + past participle | Subject + had been + present participle |
| Duration | Emphasizes the completion of an action before another past action or time | Emphasizes the duration of an action leading up to a specific point in the past |
| Completed Action | Focuses on the completion of an action | Focuses on the ongoing nature of an action leading up to a specific point in the past |
| Examples | When I arrived, they had already eaten dinner. | By the time he got home, she had been cooking for two hours. |
| Usage | Used to show that one action in the past happened before another action or time in the past | Used to show the duration of an action that began before a certain point in time in the past and continued up to that point in time |
| Emphasis | Emphasizes the completion of an action | Emphasizes the ongoing nature of an action |
