
CSEC Spanish: The Imperfect Tense
In this lesson we will discuss:
How to conjugate a verb to the imperfect tense
When the imperfect tense is used
The imperfect tense is used to say someone was doing something or a group were doing something.
Every tense in Spanish is formed first by finding the stem. This stem is usually found by removing the -ar/-er/-ir ending of the infinitive form of the verb (exceptions being irregular verbs and the subjunctive) and adding the correct ending based on the subject.
In that way, (regular) verbs are sort of like open-faced sandwiches, with the stem being the bread and the ending being the topping.

Above is the open-faced sandwich for the verb lavar. The stem, our bread, is lav-, and the ending is -ar, since it is in the infinitive. But considering that this is only a lettuce sandwich, it wouldn't really have a flavour at all.
However, when we form the imperfect tense, we switch out this lettuce so that we can add something a bit more tasty.
There are a different set of endings for -ar and -er/-ir verbs.
The endings for the imperfect tense are as follows for -ar verbs:
Yo -aba
tú -abas
él/ella/usted -aba
nosotros -ábamos
vosotros -abais
ellos/ellas/ustedes -aban
The endings for the imperfect tense are as follows for -er/-ir verbs:
Yo -ía
tú -ías
él/ella/usted -ía
nosotros -íamos
vosotros -íais
ellos/ellas/ustedes -ían
For example, the verb lavar again. When we remove the ending (our flavourless lettuce topping) we're left with the stem, lav-. So, all we need then is a subject to know which ending to use.

This translates to I was washing. (Yo lavaba).
In this sandwich, we used the subject yo, and switched out the infinitive ending (lettuce) for the imperfect tense ending for yo (cheese). Again, cheese on bread might not seem very appetizing to you, but, you have to admit, it's better than just lettuce.
Now, we can do the same with an -ir/-er verb. For this sandwich, we will use the verb decir (to say/tell) and conjugate it to the 2nd person singular in the imperfect tense (tú).

This translates to: You were saying (Tú decías) .
Here, we have the infinitive decir. So, we remove the -ir ending (lettuce) and that leaves us with our stem dec- (a slab of white bread). Then, we add the 2nd person singular ending in the imperfect tense, -ías (the non-descript slab of 'meat' on the right).
This formula remains the same for basically every verb except for these three: ver, ir and ser.
These three are the only irregular verbs in the imperfect tense.
ver
yo veía
tú veías
él/ella/usted veía
nosotros veíamos
vosotros veíais
ellos/ellas/ustedes veían
ir
yo iba
tú ibas
él/ella/usted iba
nosotros íbamos
vosotros íbais
ellos/ellas/ustedes iban
ser
yo era
tú eras
él/ella/usted era
nosotros éramos