The Uses of the Imperfect - Part I

Unlike the preterite, there are only three verbs that are irregular in the imperfect. These verbs are ir (to go), ser (to be) and ver (to see). Their conjugations are

iba, ibas, iba, íbamos, ibais, iban;
era, eras, era, éramos, erais, eran; and
veía, veías, veía, veíamos, veíais, veían respectively.

All the other verbs are regular in the imperfect. These are their endings, which replace the endings of the infinitive –ar, er and –ir.