As one of Spanish's two simple past tenses, the imperfectindicative has a conjugation that is essential to learn. It is the verb form used most often to describe conditions as they existed in the past, to provide background to events and to describe habitual actions.

As is the case with some of the other conjugation forms, the imperfect indicative forms are made by removing the infinitive ending of the verb (-ar, -er or -ir) and replacing it with an ending that indicates who is performing the action of the verb.

To take one example, the infinitive form of the verb that means "to study" is estudiar. Its infinitive ending is -ar, leaving the stem of estudi-. To say "I was studying," add -aba to the stem, forming estudiaba. To say "you were studying" (singular informal), add -abas to the stem, forming estudiabas. Other forms exist for other persons. (Note: In this lesson, the forms "was studying," "was learning" and so on are used to translate the imperfect indicative. Other translations also could be used, such as "used to study" or even "studied." The translation used depends on the context.)

The endings are quite different for verbs that end in -er and -ir, but the principle is the same. Remove the infinitive ending, then add the appropriate ending to the remaining stem.

The following chart shows the conjugations for each of the three infinitive types. The added endings for each verb are indicated in boldface. The pronouns, often not needed in sentences, are included here for clarity.

-ar verbs using estudiar (to study) as an example

• yo estudiaba (I was studying)
• tú estudiabas (you were studying)
• él/ella/usted estudiaba (he was studying, she was studying, you were studying)
• nosotros/nosotras estudiábamos (we were studying)
• vosotros/vosotras estudiabais (you were studying)
• ellos/ellas/ustedes estudiaban (they were studying, you were studying)

-er verbs using aprender (to learn) as an example

• yo aprendía (I was learning)
• tú aprendías (you were learning)
• él/ella/usted aprendía (he was learning, she was learning, you were learning)
• nosotros/nosotras aprendíamos (we were learning)
• vosotros/vosotras aprendíais (you were learning)
• ellos/ellas/ustedes aprendían (they were learning, you were learning)

-ir verbs using escribir (to write) as an example

• yo escribía (I was writing)
• tú escribías (you were writing)
• él/ella/usted escribía (he was writing, she was writing, you were writing)
• nosotros/nosotras escribíamos (we were writing)
• vosotros/vosotras escribíais (you were writing)
• ellos/ellas/ustedes escribían (they were writing, you were writing)

As you may notice, the -er and -ir verbs follow the same pattern in the imperfect indicative. Also, the first- and third-person singular forms (the "I" and "he/she/it/you" forms) are the same. Thus estudiaba could mean "I was studying," "he was studying," "she was studying" or "you were studying." If the context doesn't otherwise indicate, a pronoun or subject noun is used before the verb in such cases to indicate who is performing the action.

Note also that the conjugations above are for verbs that follow the regular conjugation. Fortunately, very few verbs are irregular in this tense.

Here are some examples of sentences that use the imperfect indicative, which is indicated in boldface. Note how the translation can vary with context:

• Llamó a la policía mientras yo compraba drogas. She called the police while I was buying drugs.
• Se saturaba el aire con olores. The air was saturated with odors.
• ¿Qué hacían los famosos antes de convertirse en estrellas? What did the famous people do before they became stars?
• Los indígenas vivíamos en un estado de infrahumanidad. We indigenous people lived a state of subhumanity.