Mastering Spanish Stem-Changing Verbs: A Comprehensive Guide

Spanish stem-changing verbs can seem daunting to language learners, but understanding their patterns is crucial for fluency. These verbs, which alter their stem vowel in certain conjugations, are extremely common and appear in everyday conversation.

This comprehensive guide breaks down the rules, patterns, and exceptions of stem-changing verbs, providing you with the knowledge and practice you need to master them. Whether you’re a beginner or an advanced learner, this article will enhance your understanding and use of Spanish verbs.

Table of Contents

• Introduction
• Definition of Stem-Changing Verbs
• Structural Breakdown
• Types of Stem Changes
  • E to IE
  • O to UE
  • E to I
  • U to UE
• Examples of Stem-Changing Verbs
  • E to IE Examples
  • O to UE Examples
  • E to I Examples
• Usage Rules
• Common Mistakes
• Practice Exercises
  • Exercise 1: E to IE
  • Exercise 2: O to UE
  • Exercise 3: E to I
• Advanced Topics
• FAQ
• Conclusion

Introduction

Stem-changing verbs are a vital part of Spanish grammar. They are verbs whose stem, the part of the verb that remains after removing the infinitive ending (-ar, -er, -ir), changes its vowel in certain conjugations.

Mastering these verbs is essential for accurate and fluent communication in Spanish. This guide will provide a clear and structured approach to understanding and using stem-changing verbs correctly.

This knowledge is particularly useful for students learning Spanish, travelers planning a trip to Spanish-speaking countries, and anyone looking to improve their Spanish language skills.

Definition of Stem-Changing Verbs

Stem-changing verbs, also known as root-changing verbs or boot verbs, are verbs in which the vowel in the stem changes depending on the verb tense and the pronoun being used. This change only occurs in certain forms of the present tense, present subjunctive, and sometimes in the preterite. The stem change typically affects all forms except for nosotros and vosotros in the present tense. The stem is the part of the verb that remains after removing the infinitive ending (-ar, -er, -ir). For example, in the verb pensar (to think), the stem is pens-. The stem change affects the vowel within this stem.

Structural Breakdown

The stem of a verb is the part that carries the main meaning. To identify the stem, remove the infinitive ending (-ar, -er, or -ir) from the verb. For instance, in the verb volver (to return), the stem is volv-. Stem changes occur in the present tense for all forms except nosotros and vosotros. The stem change affects the vowel within the stem. This means that the vowel within the verb stem will change to another vowel or diphthong depending on the verb type. These changes are predictable based on the type of stem-changing verb.

For example, consider the verb poder (to be able to). The stem is pod-. This is an O to UE stem-changing verb. Therefore, the ‘o’ in the stem changes to ‘ue’ in most conjugations. Let’s look at the full conjugation in the present tense:

• Yo puedo (I can)
• Tú puedes (You can)
• Él/Ella/Usted puede (He/She/You can)
• Nosotros/Nosotras podemos (We can)
• Vosotros/Vosotras podéis (You can)
• Ellos/Ellas/Ustedes pueden (They/You can)

Notice how the stem changes from pod- to pue- in all forms except for nosotros and vosotros. This is the core of how stem-changing verbs function.

Types of Stem Changes

There are primarily three main types of stem changes in Spanish verbs. These are:

1. E to IE
2. O to UE
3. E to I
4. U to UE

E to IE

In E to IE stem-changing verbs, the e in the stem changes to ie in all forms except nosotros and vosotros in the present tense. This is one of the most common types of stem changes. These verbs often express thoughts, feelings, or beginnings.

O to UE

In O to UE stem-changing verbs, the o in the stem changes to ue in all forms except nosotros and vosotros in the present tense. This type is prevalent among verbs describing actions or states of being.

E to I

For E to I stem-changing verbs (mostly -ir verbs), the e in the stem changes to i in all forms except nosotros and vosotros in the present tense. This change also applies in the preterite (specifically in the third-person singular and plural forms) and the present subjunctive.

U to UE

A very small number of verbs change u to ue. The most common verb of this type is jugar (to play). This change only happens with the verb jugar.

Examples of Stem-Changing Verbs

Let’s explore each type of stem-changing verb with specific examples and conjugations.

E to IE Examples

Here are some common E to IE stem-changing verbs:

• Pensar (to think)
• Querer (to want)
• Empezar (to begin)
• Comenzar (to start)
• Preferir (to prefer)
• Sentir (to feel)
• Mentir (to lie)
• Advertir (to warn)
• Hervir (to boil)
• Convertir (to convert)
• Defender (to defend)
• Descender (to descend)
• Encender (to light)
• Entender (to understand)
• Perder (to lose)
• Recomendar (to recommend)
• Negar (to deny)

Here is a table showing the conjugation of pensar (to think) in the present tense:

Pronoun	Conjugation
Yo	Pienso
Tú	Piensas
Él/Ella/Usted	Piensa
Nosotros/Nosotras	Pensamos
Vosotros/Vosotras	Pensáis
Ellos/Ellas/Ustedes	Piensan

Notice the stem change from pens- to piens- in all forms except for nosotros and vosotros. The ‘e’ changes to ‘ie’.

Here is a table with more examples using different E to IE stem-changing verbs:

Verb	Yo	Tú	Él/Ella/Usted	Nosotros/Nosotras	Vosotros/Vosotras	Ellos/Ellas/Ustedes
Querer (to want)	Quiero	Quieres	Quiere	Queremos	Queréis	Quieren
Empezar (to begin)	Empiezo	Empiezas	Empieza	Empezamos	Empezáis	Empiezan
Preferir (to prefer)	Prefiero	Prefieres	Prefiere	Preferimos	Preferís	Prefieren
Sentir (to feel)	Siento	Sientes	Siente	Sentimos	Sentís	Sienten
Mentir (to lie)	Miento	Mientes	Miente	Mentimos	Mentís	Mienten
Advertir (to warn)	Advierto	Adviertes	Advierte	Advertimos	Advertís	Advierten
Hervir (to boil)	Hiervo	Hierves	Hierve	Hervimos	Hervís	Hierven
Convertir (to convert)	Convierto	Conviertes	Convierte	Convertimos	Convertís	Convierten
Defender (to defend)	Defiendo	Defiendes	Defiende	Defendemos	Defendéis	Defienden
Descender (to descend)	Desciendo	Desciendes	Desciende	Descendemos	Descendéis	Descienden
Encender (to light)	Enciendo	Enciendes	Enciende	Encendemos	Encendéis	Encienden
Entender (to understand)	Entiendo	Entiendes	Entiende	Entendemos	Entendéis	Entienden
Perder (to lose)	Pierdo	Pierdes	Pierde	Perdemos	Perdéis	Pierden
Recomendar (to recommend)	Recomiendo	Recomiendas	Recomienda	Recomendamos	Recomendáis	Recomiendan
Negar (to deny)	Niego	Niegas	Niega	Negamos	Negáis	Niegan

O to UE Examples

Here are some common O to UE stem-changing verbs:

• Poder (to be able to)
• Volver (to return)
• Dormir (to sleep)
• Almorzar (to have lunch)
• Contar (to count, to tell)
• Costar (to cost)
• Encontrar (to find)
• Mostrar (to show)
• Probar (to try, to taste)
• Recordar (to remember)
• Resolver (to solve)
• Soler (to usually do)
• Morder (to bite)
• Oler (to smell)
• Rodar (to roll)
• Sonar (to sound, to ring)
• Tostar (to toast)
• Tronar (to thunder)

Here is a table showing the conjugation of poder (to be able to) in the present tense:

Pronoun	Conjugation
Yo	Puedo
Tú	Puedes
Él/Ella/Usted	Puede
Nosotros/Nosotras	Podemos
Vosotros/Vosotras	Podéis
Ellos/Ellas/Ustedes	Pueden

Notice the stem change from pod- to pued- in all forms except for nosotros and vosotros. The ‘o’ changes to ‘ue’.

Here is a table with more examples using different O to UE stem-changing verbs:

Verb	Yo	Tú	Él/Ella/Usted	Nosotros/Nosotras	Vosotros/Vosotras	Ellos/Ellas/Ustedes
Volver (to return)	Vuelvo	Vuelves	Vuelve	Volvemos	Volvéis	Vuelven
Dormir (to sleep)	Duermo	Duermes	Duerme	Dormimos	Dormís	Duermen
Almorzar (to have lunch)	Almuerzo	Almuerzas	Almuerza	Almorzamos	Almorzáis	Almuerzan
Contar (to count, to tell)	Cuento	Cuentas	Cuenta	Contamos	Contáis	Cuentan
Costar (to cost)	Cuesto	Cuestas	Cuesta	Costamos	Costáis	Cuestan
Encontrar (to find)	Encuentro	Encuentras	Encuentra	Encontramos	Encontráis	Encuentran
Mostrar (to show)	Muestro	Muestras	Muestra	Mostramos	Mostráis	Muestran
Probar (to try, to taste)	Pruebo	Pruebas	Prueba	Probamos	Probáis	Prueban
Recordar (to remember)	Recuerdo	Recuerdas	Recuerda	Recordamos	Recordáis	Recuerdan
Resolver (to solve)	Resuelvo	Resuelves	Resuelve	Resolvemos	Resolvéis	Resuelven
Soler (to usually do)	Suelo	Sueles	Suele	Solemos	Soléis	Suelen
Morder (to bite)	Muerdo	Muerdes	Muerde	Mordemos	Mordéis	Muerden
Oler (to smell)	Huelo	Hueles	Huele	Olemos	Oléis	Huelen
Rodar (to roll)	Ruedo	Ruedas	Rueda	Rodamos	Rodáis	Ruedan
Sonar (to sound, to ring)	Sueno	Suenas	Suena	Sonamos	Sonáis	Suenan
Tostar (to toast)	Tuesto	Tuestas	Tuesta	Tostamos	Tostáis	Tuestan
Tronar (to thunder)	Trueno	Truenas	Truena	Tronamos	Tronáis	Truenan

E to I Examples

Here are some common E to I stem-changing verbs:

• Pedir (to ask for, to order)
• Servir (to serve)
• Repetir (to repeat)
• Seguir (to follow)
• Vestir (to dress)
• Competir (to compete)
• Conseguir (to get, to obtain)
• Corregir (to correct)
• Despedir (to fire, to say goodbye)
• Elegir (to choose)
• Freír (to fry)
• Impedir (to prevent)
• Medir (to measure)
• Reír (to laugh)
• Sonreír (to smile)
• Teñir (to dye)

Here is a table showing the conjugation of pedir (to ask for) in the present tense:

Pronoun	Conjugation
Yo	Pido
Tú	Pides
Él/Ella/Usted	Pide
Nosotros/Nosotras	Pedimos
Vosotros/Vosotras	Pedís
Ellos/Ellas/Ustedes	Piden

Notice the stem change from ped- to pid- in all forms except for nosotros and vosotros. The ‘e’ changes to ‘i’.

Here is a table with more examples using different E to I stem-changing verbs:

Verb	Yo	Tú	Él/Ella/Usted	Nosotros/Nosotras	Vosotros/Vosotras	Ellos/Ellas/Ustedes
Servir (to serve)	Sirvo	Sirves	Sirve	Servimos	Servís	Sirven
Repetir (to repeat)	Repito	Repites	Repite	Repetimos	Repetís	Repiten
Seguir (to follow)	Sigo	Sigues	Sigue	Seguimos	Seguís	Siguen
Vestir (to dress)	Visto	Vistes	Viste	Vestimos	Vestís	Visten
Competir (to compete)	Compito	Compites	Compite	Competimos	Competís	Compiten
Conseguir (to get, to obtain)	Consigo	Consigues	Consigue	Conseguimos	Conseguís	Consiguen
Corregir (to correct)	Corrijo	Corriges	Corrige	Corregimos	Corregís	Corrigen
Despedir (to fire, to say goodbye)	Despido	Despides	Despide	Despedimos	Despedís	Despiden
Elegir (to choose)	Elijo	Eligies	Elige	Elegimos	Elegís	Eligen
Freír (to fry)	Frío	Fríes	Fríe	Freímos	Freís	Fríen
Impedir (to prevent)	Impido	Impides	Impide	Impedimos	Impedís	Impiden
Medir (to measure)	Mido	Mides	Mide	Medimos	Medís	Miden
Reír (to laugh)	Río	Ríes	Ríe	Reímos	Reís	Ríen
Sonreír (to smile)	Sonrío	Sonríes	Sonríe	Sonreímos	Sonreís	Sonríen
Teñir (to dye)	Tiño	Tiñes	Tiñe	Teñimos	Teñís	Tiñen

Here is the conjugation of *jugar* (to play) in the present tense:

Pronoun	Conjugation
Yo	Juego
Tú	Juegas
Él/Ella/Usted	Juega
Nosotros/Nosotras	Jugamos
Vosotros/Vosotras	Jugáis
Ellos/Ellas/Ustedes	Juegan

Usage Rules

The primary rule for stem-changing verbs is that the stem change only occurs in certain forms of the present tense, present subjunctive, and sometimes in the preterite. The nosotros and vosotros forms in the present tense do not undergo stem changes. Remember that the stem change affects the vowel within the stem of the verb. It is vital to memorize which verbs undergo stem changes and what the changes are.

Another rule is that only verbs ending in -ar, -er, and -ir can be stem-changing verbs, though not all -ar, -er, and -ir verbs are stem-changing. It is crucial to learn the specific verbs that have stem changes.

When dealing with verbs that have two ‘e’s in the stem (like preferir), the stem change affects the ‘e’ closest to the end of the verb. Thus, preferir becomes prefiero, not priefiero.

Common Mistakes

One common mistake is applying the stem change to the nosotros and vosotros forms. Remember, these forms do not undergo stem changes in the present tense.

Incorrect: Nosotros piensemos.

Correct: Nosotros pensamos.

Another mistake is using the incorrect stem change. For example, confusing E to IE with E to I.

Incorrect: Yo pido (when meaning “I think,” intending to use pensar).

Correct: Yo pienso.

Another frequent error is forgetting to stem-change when necessary.

Incorrect: Él puede volver.

Correct: Él puede volver.

Another common mistake is applying the stem change to the wrong part of the verb.

Incorrect: Yo entendio.

Correct: Yo entiendo.

Practice Exercises

Test your knowledge with the following exercises. Fill in the blanks with the correct form of the verb.

Exercise 1: E to IE

Conjugate the verb in parentheses into the correct present tense form.

Question	Answer
1. Yo ________ (pensar) que es una buena idea.	Pienso
2. Tú ________ (querer) ir al cine?	Quieres
3. Ella ________ (empezar) a estudiar a las ocho.	Empieza
4. Nosotros ________ (preferir) el café al té.	Preferimos
5. Vosotros ________ (sentir) mucho su pérdida.	Sentís
6. Ellos ________ (mentir) sobre su edad.	Mienten
7. Yo ________ (entender) la lección.	Entiendo
8. Tú ________ (perder) las llaves a menudo.	Pierdes
9. Él ________ (recomendar) este restaurante.	Recomienda
10. Nosotros ________ (negar) la acusación.	Negamos

Exercise 2: O to UE

Conjugate the verb in parentheses into the correct present tense form.

Question	Answer
1. Yo no ________ (poder) ir a la fiesta.	Puedo
2. Tú ________ (volver) a casa tarde.	Vuelves
3. Él ________ (dormir) ocho horas cada noche.	Duerme
4. Nosotros ________ (almorzar) al mediodía.	Almorzamos
5. Vosotros ________ (contar) chistes divertidos.	Contáis
6. Ellos ________ (costar) mucho dinero.	Cuestan
7. Yo ________ (encontrar) las llaves.	Encuentro
8. Tú ________ (mostrar) tus fotos.	Muestras
9. Él ________ (probar) la comida.	Prueba
10. Nosotros ________ (recordar) los buenos tiempos.	Recordamos

Exercise 3: E to I

Conjugate the verb in parentheses into the correct present tense form.

Question	Answer
1. Yo ________ (pedir) un café.	Pido
2. Tú ________ (servir) la cena.	Sirves
3. Él ________ (repetir) la pregunta.	Repite
4. Nosotros ________ (seguir) las instrucciones.	Seguimos
5. Vosotros ________ (vestir) ropa elegante.	Vestís
6. Ellos ________ (competir) en el torneo.	Compiten
7. Yo ________ (conseguir) un buen trabajo.	Consigo
8. Tú ________ (corregir) los errores.	Corriges
9. Él ________ ( corregir) los errores.	Corrige
10. Nosotros ________ (despedir) al empleado.	Despedimos

Advanced Topics

Beyond the basic stem changes, some verbs have irregular forms or additional complexities. For example, some verbs have stem changes in the preterite tense as well as the present tense. Verbs like sentir (to feel) change from e to i in the third-person singular and plural preterite forms (sintió, sintieron).

Some verbs also have irregular “yo” forms in addition to stem changes. For example, the verb hacer (to do) is irregular in the “yo” form (yo hago) and does not follow the typical stem-changing rules.

Reflexive verbs can also be stem-changing. For instance, despertarse (to wake up) is a reflexive verb that also undergoes an O to UE stem change (me despierto, te despiertas, etc.).

FAQ

Conclusion

Mastering stem-changing verbs is a significant step towards fluency in Spanish. By understanding the patterns, rules, and exceptions, you can confidently use these verbs in conversation and writing.

Remember to practice regularly and pay attention to the conjugations. With dedication and consistent effort, you’ll find that stem-changing verbs become second nature.