- 描述以過去式來寫的故事背景，例如："The sun was shining and the birds were singing as the elephant came out of the jungle. The other animals were relaxing in the shade of the trees, but the elephant moved very quickly. She was looking for her baby, and she didn't notice the hunter who was watching her through his binoculars. When the shot rang out, she was running towards the river..."
- 描述未完成的動作，這個動作被另一個動作或事件給打斷了。例如："I was having a beautiful dream when the alarm clock rang."
- 表達改變心意。例如："I was going to spend the day at the beach but I've decided to get my homework done instead."
- 與「wonder」連用，讓要求的語氣變得很客氣。例如："I was wondering if you could baby-sit for me tonight."
- They were waiting for the bus when the accident happened.
- Caroline was skiing when she broke her leg.
- When we arrived he was having a bath.
- When the fire started I was watching television.
任何動詞的過去進行式都是以兩個要素構成：Be 動詞的過去式 (was/were)，以及主要動詞原型 +ing。
|主詞||was/were||動詞原型 + ing|
過去進行式，以 to play 為例
|I was playing||I was not playing||Was I playing?|
|You were playing||You were not playing||Were you playing?|
|He was playing||He wasn't playing||Was he playing?|
|We were playing||We weren't playing||Were we playing?|
|They were playing||They weren't playing||Were they playing?|