How to Conjugate Stem-changing Verbs in Spanish

Many years ago, Endel Tulving, a phycologist, discovered something that can help you memorize the conjugation of Spanish irregular verbs.

Would you like to know what that is? I will tell you more about it later in the lesson. First, I would like to share with you what stem-changing verbs are and how you can conjugate them.

Irregular Verbs

A Spanish irregular verb is a verb that suffers a change in its stem when it is conjugated. 

A verb stem is the root of a verb. For example, in the verb amar, am is the stem, and ar is the ending. 

In Spanish, all verbs end in one of three ways: -ar, -er, -ir. Eliminate the ending of a verb, and all you are left with is its stem. 

In Spanish, a verb is considered irregular when there is a change in its stem when conjugated. If the stem of a verb does not change when the verb is conjugated, then, it is considered a regular verb. 

Let’s practice a bit! What’s the stem of the verb querer (to love)? It’s quer. When conjugated, the verb querer changes to quiero (I love), for example. Is querer a regular or an irregular verb in Spanish? Yes, it’s irregular! Its stem changes, for the vowel i is added in quer.

Oh! The verbs we are about to study are also called “boot verbs.” Have you ever wondered why? It’s because when they are conjugated and placed in a conjugation table, the only verbs that suffer a stem change form a boot. 

That kind of looks like a boot, doesn’t it?

Notice in the chart that the nosotros and vosotros forms are not affected by this stem change in the present tense. The vos form is not affected by this change either.

IRREGULAR -AR VERBS

Verbs that end in -ar have two possible changes in their stem. Here they are!

Change E > IE

If an irregular verb has the vowel e in the second last syllable, change the vowel e for ie.

Pensar (to think)

• Yo pienso

• Tú  piensas
• Vos pensas

• Él piensa
• Ella piensa
• Usted piensa

• Nosotros pensamos
• Nosotras pensamos

• Vosotros pensáis
• Vosotras pensáis

• Ellos piensan
• Ellas piensan
• Ustedes piensan

Change O > UE

If an irregular verb has the vowel o in the second last syllable, change the o for ue.

Recordar (to remember)

• Yo recuerdo

• Tú  recuerdas
• Vos recordás

• Él recuerda
• Ella recuerda
• Usted recuerda

• Nosotros recordamos
• Nosotras recordamos

• Vosotros recordáis
• Vosotras recordáis

• Ellos recuerdan
• Ellas recuerdan
• Ustedes recuerdan

IRREGULAR -ER VERBS

Verbs that end in -er have two possible changes in their stem as well. However, in this category, there are verbs that change in the yo form only. I’ll show them to you. 

Change E > IE

If an irregular -er verb has the vowel e in the second last syllable, change the vowel e for ie. 

Querer (to want)

• Yo quiero

• Tú  quieres
• Vos querés

• Él quiere
• Ella quiere
• Usted quiere

• Nosotros queremos
• Nosotras queremos

• Vosotros queréis
• Vosotras queréis

• Ellos quieren
• Ellas quieren
• Ustedes quieren

Change O > UE

If an irregular -er verb has the vowel o in the second last syllable, change the o for ue.

Poder (to be able to / can)

• Yo puedo

• Tú  puedes
• Vos podés

• Él puede
• Ella puede
• Usted puede

• Nosotros podemos
• Nosotras podemos

• Vosotros podéis
• Vosotras podéis

• Ellos pueden
• Ellas pueden
• Ustedes pueden

Irregular in the yo form only

The following verbs suffer a change in their stem only in the yo form.

• poner (to put) – yo pongo

• saber (to know) – yo sé

• ver (to see) – yo veo

• nacer (to be born) – yo nazco

• agradecer (to thank) – yo agradezco

• conocer (to meet) – yo conozco

IRREGULAR -IR VERBS

These verbs have three common changes in their stem. Here they are!

Change E > IE

At times, the second last vowel e in irregular -ir verb changes to ie.

Preferir (to prefer)

• Yo prefiero

• Tú  prefieres
• Vos preferís

• Él prefiere
• Ella prefiere
• Usted prefiere

• Nosotros preferimos
• Nosotras preferimos

• Vosotros preferís
• Vosotras preferís

• Ellos prefieren
• Ellas prefieren
• Ustedes prefieren

Change E > I

And some other times, the second last vowel e is replaced only by the vowel i.

Pedir (to ask for)

• Yo pido

• Tú  pides
• Vos pedís

• Él pide
• Ella pide
• Usted pide

• Nosotros pedimos
• Nosotras pedimos

• Vosotros pedís
• Vosotras pedís

• Ellos piden
• Ellas piden
• Ustedes piden

Change O > UE

I could only find two verbs in this category, the verbs dormir (to sleep) and morir.(to die). In here, you need to change the vowel o to ue.

Dormir (to sleep)

• Yo duermo

• Tú  duermes
• Vos dormís

• Él duerme
• Ella duerme
• Usted duerme

• Nosotros dormimos
• Nosotras dormimos

• Vosotros dormís
• Vosotras dormís

• Ellos duermen
• Ellas duermen
• Ustedes duermen

Here’s a little chart that summarizes what we have learned so far!

Irregular Verb Chart

Remember Endel Tulving and his discovery? Well, he formed two groups of students and gave each group 100 cards with words printed on them.

He asked one group to memorize the cards. The other group was asked to organize the cards into categories. The results surprised Endel! When tested, both groups remembered the vocabulary with the same precision.

Yes, organizing stem-changing verbs into a few categories can help you remember their conjugation!

So, what do you think? Do you dare to try organizing some irregular verbs into a few categories?

Download the PDF to get the answers.