How to Conjugate Stem-changing Verbs in Spanish

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

He made an experiment with two groups of students, and the results surprised him a bit. I will tell you more about this later in the lesson.

First, let me share with you what irregular verbs or stem-changing verbs are and how you can conjugate them.

Stem Changing 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.

-AR VERBS

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

Stem Change E > EI

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

Remember that the forms nosotros and vosotros (abbreviated nos. and vos. below) are not affected by this change.

PENSAR – TO THINK

Examples

To conjugate the following verbs in the simple present tense, use the pensar conjugation model.

• acertar (guess)
• alentar (encourage)
• apretar (tighten)
• arrendar (rent)
• asentar (settle)
• aterrar (terrify)
• atravesar (cross)
• calentar (heat)
• cegar (blind)
• cerrar (close)
• comenzar (start)
• concertar (conclude)
• confesar (confess)
• denegar (deny)
• desalentar (discourage)
• desconcertar (confuse)
• desenterrar (dig up)
• deshelar (defrost)
• despertar (wake up)
• desplegar (display)
• desterrar (expatriate)
• emparentar (relate)
• empezar (begin)
• encerrar (confine)
• encomendar (entrust)
• enmendar (amend)
• enterrar (bury)
• gobernar (govern)
• helar (freeze)
• invernar (winter)
• manifestar (express)
• mentar (mention)
• merendar (eat an afternoon snack)
• negar (deny)
• nevar (impersonal verb “to snow”)
• quebrar (brake)
• recalentar (reheat)
• recomendar (recommend)
• regar (water)
• remendar (patch)
• renegar (deny)
• restregar (scrub)
• reventar (burst)
• salpimentar (season with salt and pepper)
• segar (reap)
• sembrar (sow)
• sentar (seat)
• serrar (saw)
• sosegar (calm)
• soterrar (underground)
• temblar (shake)
• tentar (tempt)
• tropezar (trip)

Stem Change O > UE

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

RECORDAR – TO REMEMBER

Examples

To conjugate the following verbs in the simple present tense, use the recordar conjugation model.

• acordar (agree)
• apostar (bet)
• aprobar (approve)
• asolar (destroy)
• colar (strain)
• comprobar (check)
• concordar (agree)
• consolar (comfort)
• contar (count)
• costar (cost)
• demostrar (demonstrate)
• desaprobar (disapprove)
• descontar (discount)
• encontrar (find)
• engrosar (swell)
• mostrar (show)
• poblar (populate)
• probar (try)
• recostar (tilt)
• renovar (renew)
• repoblar (repopulate)
• reprobar (fail)
• resonar (resonate)
• rodar (roll)
• sobrevolar (overfly)
• soldar (weld)
• soltar (release)
• sonar (sound)
• soñar (dream)
• tostar (toast)
• tronar (impersonal verb “to thunder”)
• volar (fly)
• volcar (overturn)

-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. 

Stem Change E > EI

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

QUERER – TO LOVE

Examples

To conjugate the following verbs in the simple present tense, use the querer conjugation model.

• ascender (promote)
• atender (attend)
• defender (defend)
• desatender (neglect)
• descender (descend)
• encender (turn on)
• entender (understand)
• extender (extend)
• perder (lose)
• tender (tend)
• trascender (transcend)
• verter (pour)

Stem 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

Examples

To conjugate the following verbs in the simple present tense, use the poder conjugation model.

• absolver (absolve)
• conmover (stir)
• demoler (demolish)
• desenvolver (unfold)
• devolver (return)
• disolver (dissolve)
• doler (hurt)
• envolver (wrap)
• llover (impersonal verb “to rain”)
• moler (grind)
• morder (bite)
• mover (move)
• promover (promote)
• remorder (chew)
• remover (remove)
• resolver (solve)
• revolver (scramble)

Irregular in the yo form only

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

HACER – TO DO, MAKE

Examples

Use the hacer conjugation model to conjugate the following verbs in the simple prensent tense with the rest of the Spanish pronouns.

• poner (put) – yo pongo
• saber (know) – yo sé
• ver (see) – yo veo
• nacer (be born) – yo nazco
• agradecer (thank) – yo agradezco
• conocer (meet) – yo conozco

-IR Verbs

The conjugation of some irregular -ir verbs is a bit tricky, so pay special attention here.

These verbs have three common changes in their stem. Oh! And there are some verbs that have a change in their stem in the yo form only as well. 

Stem Change E > EI

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

PREFERIR – TO PREFER

Examples

To conjugate the following verbs in the simple present tense, use the preferir conjugation model.

• mentir (lie)
• concernir (concern)
• adherir (adhere, attach)
• adquirir (acquire, buy)
• diferir (differ, defer)
• digerir (digest, absorb)
• herir (hurt, injure)
• inferir (infer, conclude)
• ingerir (eat, ingest) 
• interferir (interfere)
• preferir (prefer) 
• referir (refer, relate)
• transferir (transfer, assign)
• discernir (discern)
• divertir (entertain, amuse) 
• sentir (feel, sense)
• revertir (reverse, revert)
• resentir (resent)
• presentir (sense)
• invertir (invest)

Stem Change E > I

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

PEDIR – TO ASK

Examples

To conjugate the following verbs in the simple present tense, use the pedir conjugation model.

• seguir (follow)
• sonreír (smile)
• repetir (repeat)
• teñir (dye)
• elegir (choose)
• regir (govern)
• pedir (ask)
• derretir (melt)
• despedir (dismiss)
• freír (fry)
• gemir (groan)
• impedir (prevent)
• servir (help)
• repetir (repeat)
• rendir (render)
• reñir (quarrel)
• medir (measure)
• vestir (dress)

Stem Change O > UE

I could only find two verbs that fall into this category. In here, you need to change the vowel o to ue in the following verbs.

DORMIR – TO SLEEP

Examples

Use the dormir conjugation model to conjugate the following verb in the present tense.

• morir (die)

Irregular in the yo form only

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

SALIR – TO LEAVE

Examples

I would recommend you to check the complete conjugation of  “oir” and “reducir,” since both verbs have unique conjugation patterns. Just click on the verbs below to check it out.

• oir (listen) – yo oigo
• reducir (reduce) – yo reduzco

And that’s it! Now you know how to use stem-changing verbs in the present. 

Here’s a chart that summarises what we just learned! Oh! If you would like to get a printable PDF of the chart, click the download button below.

Irregular Verbs: List and Practice

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?