1. An action which was in progress at a particular time in the past.
Example: I was studying English yesterday afternoon.
2. An action in the past that is interrumpted by another action.
Example: I was watching TV when he knocked the door.
- Affirmative: subject + was/were + verb -ing + complements
- Negative: subject + wasn't/weren't + verb -ing + complements
- Question: was/were + subject + verb -ing + complements?
- A specific moment in the past. For example: I was playing football yesterday afternoon.
- When /While