The Imperfect is used to express long term, habitual or background actions as well as for descriptions and simultaneous actions happened in the past. This tense is specific to Spanish and there is not an exact counterpart in English.

(See comparison between PRETERIT and IMPERFECT here)

Examples:

• Había un partido de fútbol cada sábado (There was a soccer game every Saturday)

• Mientras yo leía,  my hermano escribía (While I was reading my brother was writing)

• Eranlas once de la noche y hacía mucho frío (It was 11 pm and it was too cold)

• Ellos tenían alrededor de 15 o 16 años (They were around 15 or 16 years old)

• En ese tiempo, solía hacer más ejercicio (At that time, I was used to do more exercise)

The Imperfect conjugation of model regular verbs (ar, er, ir) is: