There are no spelling changes and no stem changes in the imperfect. The – ar endings found in Table 1 are used for every – ar verb in the entire language. There is not a single – ar verb that is irregular in the imperfect tense. Notice that the yo form is exactly like the él, ella, and usted forms, so it is important to use the pronoun or noun to specify what the subject is in a specific sentence. Also notice that only the nosotros/nosotras form has a written accent mark.
A stem‐changing verb like pensar (to think) will not have any stem change in the imperfect. As you can see in Table 2, the verb pensar is completely regular in the imperfect tense.
The verb trabajar (to work) looks really strange in the imperfect tense, but it also is a good example that all forms of all – ar verbs are regular in the imperfect tense. Read Table 3 outloud because it's fun to say the imperfect tense forms of the verb trabajar.
The endings in Table 4 are the regular endings for both – er and – ir verbs. There are only three irregular verbs in the imperfect tense: ser, ir, and ver. For every other – er and – ir verb, use the endings in Table 4. Notice that all imperfect tense forms of – er and – ir verbs have a written accent mark on the letter i.
The – er verbs use the exact same endings in the imperfect tense as the – ir verbs, so look at perder as another good example and notice in Table 5 that perder does not stem change in the imperfect tense.
A regular verb like vivir (to live) conjugated in Table 6 serves as a good example of an – ir verb in the imperfect tense.
The verb sentir (to feel, to regret) is a stem changer in the present tense, but Table 7 will remind you that no verbs stem change in the imperfect tense.