Aspect imperfectif

French Imperfective Aspect

The imperfective aspect indicates an action, event or state that was, is, or will be incomplete, in the past, present or future. It describes the process of the situation, its internal temporal structure.  

If you say Je lisais ce livre (= I was reading that book), you are describing that process and are probably going to follow up with what happened while you were reading it (as opposed to what happened after you read it).  

For example

Je travaille en ce moment. = I am working at the moment.
Nous regardions la télévision quand vous nous avez appelés. = We were watching television when you called us.
Je conduisais cette voiture pendant longtemps. = I drove that car for a long time.
Auparavant, je lisais beaucoup de romans à suspense. = Before, I used to read lots of thrillers.

Note that the imperfective aspect combines the progressive aspect (We were watching) and the habitual aspect (We used to watch).

In French, in the past, the imperfective aspect is usually indicated by the imperfect tense. In contrast, English might use a progressive form, a simple past form, or some other verbal construction.
 

Introduction to aspect

 

Clever stuff happening!