Stem-changing irregular verbs maintain the regular -ar, -er, and -ir conjugation endings, but the stem of the verb changes for all subject pronouns except “nosotros/nosotras”.

*Don’t remember how to conjugate regular -ar, -er, and -ir verbs? If you need to refresh, go here.

Stem-changing verbs are irregular because the root or stem of the verb changes. Take a look at the infinitive forms for the following three verbs:

Let’s see how these are conjugated in the “yo” form in the present tense:

You can see how the conjugation ending for the “yo” form doesn’t change (it’s still the “o” we’re accustomed to), but the stem of the verb changes.

In this lesson, we’ll look at the three main groups of stem-changing verbs. We can categorize these verbs by the change to their stem (e to ie, o to ue, and e to i). We’ll also review common stem-changing verbs for each category in the present tense.

But first, how do we know which verbs have stem changes? When you look them up in the dictionary, the change is indicated next to the verb, something like this, “pensar (e-ie)”.

Otherwise, you just have to memorize them. The good news is there are some stem-changing verbs you’ll use regularly, so it’s easy to remember them.

Verbs with e to ie stem changes.

In this category, the “e” in the verb changes to “ie” in all persons except “nosotros/nosotras”. There are -ar, -er, and -ir verbs that have this change. Let’s look at some examples in the chart below.

Notice how the “nosotros/nosotras” form does not change. It reverts to its regular verb form.

You might also be wondering how to know which “e” changes to “ie” as with “preferir”. Usually, it’s the second “e” in the verb. This happens with all stem-changing verbs regardless of the group they belong to.

There is also the verb, “adquirir”, which has a slightly different change, “i” to “ie”:

Verbs with o to ue stem changes

In this category, the “o” in the verb changes to “ue” in all persons except “nosotros/nosotras”. Just as with the “e” to “ie” change, there are -ar, -er, and -ir verbs that have this stem change. Let’s look at some examples.

There is also one verb, “jugar”, which has a “u” to “ue” change.

Verbs with e to i stem changes

In this group, the “e” in the verb changes to “i” in all persons except “nosotros/nosotras”. Only -ir verbs are in this category. Let’s look at an example.

Common stem-changing verbs

Below, we’ve listed some common stem-changing verbs. Remember, there are more out there.

Other verbs with stem changes

If a verb stems from any of the above verbs,  then it will follow the same conjugation rules.

There are irregular verbs that have stem changes AND another irregular spelling change or ending change in one or more person.  Here we have some of the most common ones.

Notice “tener” and “venir” have a change in the “yo” form also in addition to a stem change. There is no stem change in “yo” or “nosotros/nosotras” forms.

Notice there is a change in the “yo” form and stem changes in all persons except “nosotros/nosotras”.

Now let’s practice conjugating stem-changing verbs with the following quizzes.

In this lesson, we’ve covered how to conjugate stem-changing verbs.  There are three general categories of stem-changing verbs: e to ie, o to ue, and e to i.  It’s important to remember to check in a dictionary if a verb has a stem change or not.  At the end of the lesson, we listed some of the most common stem-changing verbs, the ones you’re likely to need day-to-day.  Want to learn more verbs?  Check out our post on the 45 most common verbs in Spanish.  Not sure where to go from here? Check out other parts of speech, like prepositions.