过去进行时是英语语法中的一种时态，用于表示过去某一时刻正在进行的动作。构成过去进行时的常用词语包括be动词的过去式“was”或“were”，动词的“-ing”形式，以及表示时间段的词语。例如：“I was watching TV when she called me.”、“She was cooking dinner when I arrived.”等。
be动词
过去进行时需要使用be动词的过去式“was”或“were”，来辅助动词的进行形式。
例如：
- I was watching TV when she called me.
- They were playing basketball in the park.
动词+ing形式
在过去进行时中，动词需要加上“-ing”形式，来表示动作正在进行中。
例如：
- She was cooking dinner when I arrived.
- He was studying in the library all morning.
表示时间段的词语
有些时间段的词语也可以用来表示过去进行时，如“at this time yesterday”、“at 6 pm last night”。
例如：
- At this time yesterday, I was walking my dog in the park.
- They were still working in the office at 10 pm last night.
