Some verbs are irregular in the preterit tense because the stem of the verb morphs into something very different from the infinitive. These verbs are not stem‐changers because they do not follow the patterns that stem‐changing verbs follow. The morphing verbs do, however, have consistent preterit irregularities that you can predict if you know they are morphing verbs. These verbs also consistently use the special set of irregular endings found in Table
. All the preterit‐morphing verbs listed below use these endings rather than the regular preterit endings. Notice that there are no written accent marks on any form.
Some verbs have a u as part of the stem in the preterit even though they do not have a u in the infinitive. The morph listed next to the verbs below is used in place of the stem of the verb for every form of the preterit conjugation. All of the following verbs use the endings from Table to form the preterit.
Memorize the forms of tener in the preterit (Table ) and chant them like a mantra. Not only is the verb tener (to have) extremely common, but knowing how to conjugate it in the preterit tense will also help you to remember the patterns for all of the u-stem verbs listed above.
Another group of preterit‐morphing verbs have an irregular stem that includes the letter i. These verbs use the irregular endings in Table . The i-stem verbs that follow are conjugated like venir (to come) in the preterit tense (see Table ).
Remember that preterit‐morphing verbs do not conjugate like stem‐changers in the preterit tense, even though some of them may be stem‐changers in the present tense.
Even though hacer uses the same endings as venir in the preterit, there is one spelling change that you have to make on the él, ella, and usted forms of hacer to preserve the soft c sound. As you can see in Table , you must change the c to a z in front of the ‐o ending.
The group of preterit‐morphing verbs with a stem ending in j use the same endings as the other preterit‐morphing verbs with one exception: Notice that the third‐person plural ending of the verb traer in Table is ‐eron. When the irregular stem ends in j, the ellos, ellas, and ustedes ending drops the letter i and becomes ‐jeron. All the following verbs are conjugated like traer in the preterit.