Spanish stem-changing verbs: the boot, the lists, the traps

Some Spanish verbs change a vowel in the middle as well as the ending: querer becomes quiero, poder becomes puedo. Here's which verbs do it, where, and the one past-tense change most learners miss.

What is a stem change?

Take the infinitive, drop -ar, -er or -ir, and what's left is the stem: quer-, pod-, ped-. In a stem-changing verb, the last vowel of that stem changes whenever the stress falls on it. That's why quiero (stress on the stem) changes but queremos (stress on the ending) doesn't. The endings themselves are perfectly regular.

The boot pattern

Write the six present-tense forms in two columns (singular on the left, plural on the right) and draw a line around the forms that change. You get a boot: yo, tú, él/ella/usted and ellos/ellas/ustedes are inside it; nosotros and vosotros stay outside.

Since Latin American Spanish uses ustedes instead of vosotros, you really only have one form outside the boot to remember: nosotros.

e → ie verbs

o → ue verbs

A Mexico note: recordar is correct everywhere, but in conversation people more often say No me acuerdo (I don't remember), from acordarse, which is also o → ue.

e → i verbs (only -ir verbs)

u → ue: jugar

jugar is the only verb in this group: juego, juegas, juega, jugamos, juegan. In Mexico you'll hear Juego futbol los sábados, usually written without an accent because Mexicans stress the last syllable; in Spain it's Juego al fútbol. Careful: jugo without the e is juice.

Preterite: the -ir verbs change again

This is the part most learners miss. In the preterite, -ar and -er stem-changers are completely regular (pensé, pensó; volví, volvió; entendieron). But -ir stem-changers change in the él/ella/usted and ellos/ustedes forms: e becomes i, and o becomes u.

Example: Anoche el niño durmió diez horas (Last night the boy slept ten hours). Mis amigos pidieron pizza (My friends ordered pizza). The same i and u show up in the gerund (pidiendo, sirviendo, diciendo, durmiendo, sintiendo) and in the imperfect subjunctive (pidiera, durmiera), so Estoy pidiendo un taxi is correct and pediendo isn't.

Subjunctive: one extra change for -ir verbs

In the present subjunctive the boot pattern is the same, except that -ir stem-changers also change in the nosotros form: durmamos, pidamos, sintamos, prefiramos. You'll hear this in suggestions like Pidamos la cuenta (Let's ask for the bill). The subjunctive course covers the full forms.

How do you know a verb is stem-changing?

You can't tell from the infinitive: volver changes and comer doesn't; entender changes and aprender doesn't; pensar changes and pasar doesn't. Good dictionaries mark them as pensar (ie), dormir (ue, u), pedir (i, i), where the second letter is the preterite change. The quickest fix is to learn the twenty or so common ones above, then check any new verb in the Spanish conjugator or the verb tables.

Common mistakes

• Yo quero should be Yo quiero.
• Nosotros puedemos should be Nosotros podemos. Nosotros is outside the boot.
• Ella pedió should be Ella pidió, and dormió should be durmió.
• Yo jugo should be Yo juego. Jugo is juice.
• Yo empezo should be Yo empiezo, and in the preterite empecé (z becomes c before e).
• Pensó is right; don't add a change to -ar verbs in the past (piensó doesn't exist).

If you're never sure whether you've put the change in the right place, write a few sentences about your week and run them through the free grammar checker: it flags the wrong form and shows the right one.

More from Juntos: free Spanish grammar checker · Spanish spell and accent checker · AI Spanish tutor · practice Spanish with friends · Spanish games · all grammar courses · all practice scenarios · common Spanish mistakes · Spanish false friends · Spot the slip quiz · Spanish verb conjugations · verb conjugator · best AI Spanish tutors compared · Duolingo alternatives · about Juntos · home