Spanish Preterite: Irregular Verbs

Once you start delving into the Spanish preterite, you’ll find that verbs start acting in very strange ways. Unfortunately, you are going to find many irregular verbs in the Spanish preterite tense. Many irregularities in verb conjugations occur simply because of pronunciation. Spanish, unlike English, is pronounced phonetically. In other words, you can read any word in Spanish as long as you understand how to sound it out. In order to preserve the pronunciation of certain words, the spelling of those words will change.

Irregular Verbs that End in –zar, -car, -gar

Verbs that end with -zar, -car, or –gar cannot be conjugated normally in the “yo” form of the preterite tense without having to change their spelling of necessity to preserve the pronunciation.

For example, think of the verb pescar (to fish). Try to conjugate it normally in the “yo” form: pesc + -é = pescé. The letter ‘c’ is a soft sound in Spanish, so the word would sound like pesé. In order to preserve the hard ‘k’ sound of “pescar,” Spanish changes the ‘c’ to a ‘qu,’ making the ‘yo’ form into pesqué.

The following table gives examples of some irregular verbs that change in the “yo” form to preserve the correct pronunciation. Note that the other conjugations remain regular.

(to start)

(to fish)

(to pay)








Ud., él, ella












Uds., ellos, ellas




Other verbs that change in this way include jugar (jugué) and buscar (busqué).

Por ejemplo:

Stem-Changing Verbs in the Past

Do you remember what a stem change is? A stem change is when the stem of a verb (the part that is left when the –AR, -ER, or –IR ending is taken away) changes its vowel sounds from –e to –ie, –e to –i, –o to –ue, or –o to –u.

To understand stem changes in the preterite tense, you must first note that:

1. All the —AR and —ER verbs that stem change in the present (such as mostrar, almorzar, pensar, perder, tener, and entender) do NOT stem change in the preterite.

(These verbs may be irregular in other ways, however.)

In the "Spanish Present Progressive" lesson in the Beginner’s section, you learned about stem changes in present participles, such as estoy viniendo, estoy durmiendo, and estoy diciendo.

2. The –IR stem-changing verbs WILL stem change in the preterite, but only in the third person singular and plural. They follow the same rules as the present participles, except that all –o to –ue stem changers become –o to –u, and all –e to –ie stem changers become –e to –i.

(You may feel a bit discouraged to know that these verbs may have additional irregularities, such as the verbs venir and decir, which you’ll study later on.)

All these rules may sound a bit confusing, so here are some examples.

—e to —i 

(to repeat)
—o to —u 

(to sleep)
yo repetí dormí
repetiste dormiste
Ud., él, ella repitió durmió
nosotros/as repetimos dormimos
vosotros/as repetisteis dormisteis
Uds., ellos, ellas repitieron durmieron

Other –e to –i verbs include servir, sentir, preferir, and pedir.
Other –o to –u verbs include morir.

Por ejemplo:


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