Spanish 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 Yo leía ese libro (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).
- Yo trabajaba en aquel momento. - I was working at that moment.
- Nosotros veíamos la televisión cuando nos llamaste. - We were watching television when you called us.
- El verano pasado hacía mucho calor en el pueblo.- Last summer it was very hot in the village.
- Antes, solía leer muchas novelas de suspense. - Before, I used to read lots of thrillers.
In Spanish, in the past, the imperfective aspect is usually indicated by El Pretérito Imperfecto. In contrast, English might use a progressive form, a simple past form, or some other verbal construction.