When to use it: To describe what was happening or what used to happen at a certain time in the past.
How to form it: The starting point is to know the nous form of present tense verbs. e.g:
Remove the -ons from the nous form, so that you are left with a stem:
Add the following endings to all imperfect verbs. e.g. je regardais:
There is only one exception! The imperfect stem of the verb être is ét-, used as in j'étais, etc.
Here are two expressions using imperfect verbs that are really useful: