Stem-changing verbs, also known as “shoe verbs” or “boot verbs,” change the vowel in their stem (root) when conjugated in the present tense, present subjunctive, and some other forms. They follow regular endings but the stem vowel changes. The pattern helps avoid vowel clashes and maintain pronunciation.
Categories
There are three main types of stem changes in Spanish verbs, each affecting a different vowel in the stem:
- e → ie (e changes to ie)
- o → ue (o changes to ue)
- e → i (e changes to i)
These changes occur only in certain forms of the verb—typically all singular forms (yo, tú, él/ella/usted) and all plural forms in the present tense (nosotros/as, vosotros/as forms do NOT change).
Examples with cantar (sing!)
Let’s conjugate cantar (to sing) in present tense as a baseline—cantar is a regular -ar verb, so there’s no stem change. We’ll use this to compare with irregular verbs.
<table>
<thead>
<tr>
<th>Spanish Conjugation</th>
<th>English Conjugation</th>
</tr>
</thead>
<tbody>
<tr>
<td>yo canto</td>
<td>I sing</td>
</tr>
<tr>
<td>tú cantas</td>
<td>you sing</td>
</tr>
<tr>
<td>él/ella canta</td>
<td>he/she sings</td>
</tr>
<tr>
<td>nosotros/as cantamos</td>
<td>we sing</td>
</tr>
<tr>
<td>vosotros/as cantáis</td>
<td>you all sing</td>
</tr>
<tr>
<td>ellos/as cantan</td>
<td>they sing</td>
</tr>
</tbody>
</table>
Stem Change: e → ie
Let’s use pensar (to think) to see how the stem changes:
- Stem vowel e changes to ie in all forms except nosotros/as and vosotros/as.
<table>
<thead>
<tr>
<th>Spanish Conjugation</th>
<th>English Conjugation</th>
</tr>
</thead>
<tbody>
<tr>
<td>yo pienso</td>
<td>I think</td>
</tr>
<tr>
<td>tú piensas</td>
<td>you think</td>
</tr>
<tr>
<td>él/ella piensa</td>
<td>he/she thinks</td>
</tr>
<tr>
<td>nosotros/as pensamos</td>
<td>we think</td>
</tr>
<tr>
<td>vosotros/as pensáis</td>
<td>you all think</td>
</tr>
<tr>
<td>ellos/as piensan</td>
<td>they think</td>
</tr>
</tbody>
</table>
Stem Change: o → ue
Use the verb dormir (to sleep):
- Stem vowel o changes to ue in all forms except nosotros/as and vosotros/as.
<table>
<thead>
<tr>
<th>Spanish Conjugation</th>
<th>English Conjugation</th>
</tr>
</thead>
<tbody>
<tr>
<td>yo duermo</td>
<td>I sleep</td>
</tr>
<tr>
<td>tú duermes</td>
<td>you sleep</td>
</tr>
<tr>
<td>él/ella duerme</td>
<td>he/she sleeps</td>
</tr>
<tr>
<td>nosotros/as dormimos</td>
<td>we sleep</td>
</tr>
<tr>
<td>vosotros/as dormís</td>
<td>you all sleep</td>
</tr>
<tr>
<td>ellos/as duermen</td>
<td>they sleep</td>
</tr>
</tbody>
</table>
Stem Change: e → i
Use the verb pedir (to ask for/order):
- Stem vowel e changes to i in all forms except nosotros/as and vosotros/as.
<table>
<thead>
<tr>
<th>Spanish Conjugation</th>
<th>English Conjugation</th>
</tr>
</thead>
<tbody>
<tr>
<td>yo pido</td>
<td>I ask for</td>
</tr>
<tr>
<td>tú pides</td>
<td>you ask for</td>
</tr>
<tr>
<td>él/ella pide</td>
<td>he/she asks for</td>
</tr>
<tr>
<td>nosotros/as pedimos</td>
<td>we ask for</td>
</tr>
<tr>
<td>vosotros/as pedís</td>
<td>you all ask for</td>
</tr>
<tr>
<td>ellos/as piden</td>
<td>they ask for</td>
</tr>
</tbody>
</table>
Conjugate pedir for 'they ask for' (ellas).
ellas piden
The stem vowel e changes to i in the third-person plural, so the form is 'ellas piden'.
Conjugate pedir for 'we ask for' (nosotros).
nosotros pedimos
The nosotros form does not undergo the stem change, so it remains 'nosotros pedimos'.
Special Case: jugar (u → ue)
Most stem changes occur with e or o, but jugar (to play) changes u to ue:
<table>
<thead>
<tr>
<th>Spanish Conjugation</th>
<th>English Conjugation</th>
</tr>
</thead>
<tbody>
<tr>
<td>yo juego</td>
<td>I play</td>
</tr>
<tr>
<td>tú juegas</td>
<td>you play</td>
</tr>
<tr>
<td>él/ella juega</td>
<td>he/she plays</td>
</tr>
<tr>
<td>nosotros/as jugamos</td>
<td>we play</td>
</tr>
<tr>
<td>vosotros/as jugáis</td>
<td>you all play</td>
</tr>
<tr>
<td>ellos/as juegan</td>
<td>they play</td>
</tr>
</tbody>
</table>
Other Tenses and Moods
Stem changes also appear in:
- Present subjunctive: e.g., que yo piense, que ellos duerman, que yo pida
- Imperative (command) forms: e.g., ¡piensa!, ¡duerme!, ¡pide!
- Past participle and other irregular forms (rarely)
Summary
Stem-changing verbs in Spanish modify the vowel in their stem to maintain pronunciation and ease of speech. The changes follow these general rules:
- e → ie (pensar, entender, preferir)
- o → ue (dormir, poder, volver)
- e → i (pedir, repetir, servir)
- The changes occur in all singular and third-person plural forms in present indicative and subjunctive.
- Nosotros/as and vosotros/as forms remain regular (no stem change).
This understanding helps you confidently conjugate common irregular verbs and recognize patterns in Spanish grammar.
Last updated: Wed Jun 18, 2025
