Spanish stem-changing verbs: e→ie, o→ue, e→i

The three stem changes, in one chart

The rule is about stress, not about the verb's ending. In pienso, piensas, piensa and piensan the stress falls on the stem, and the stem's e opens into ie. In pensamos and pensáis the stress moves to the ending and the e stays. The o of poder does the same — puedo, but podemos — and in a smaller group of -ir verbs the e closes to i instead: pido, but pedimos. The academies' grammar calls the e/ie switch perhaps the most general and constant feature of the Spanish verb system.

That is why teachers call them boot verbs, or shoe verbs: on a conjugation chart the four forms that change — yo, tú, él and ellos — make the outline of a boot, and nosotros and vosotros are left outside it. The infinitive is stressed on its ending too, so it never shows the change: you learn it with the verb.

Two changes belong to almost no other verb: jugar is the only one that turns u into ue (juego, jugamos), and adquirir and inquirir are the only two that turn i into ie (adquiero, adquirimos).

Which verbs are stem-changing? The common ones

Nothing in the infinitive tells you which verbs change: empezar does (empiezo) and llegar does not (llego); contar does (cuento) and comer does not (como). The change is learned with the verb.

The e → i change lives only in -ir verbs: the grammar names the ones ending in -edir, -egir, -eguir, -eñir, -estir and -etir, the ones in -eír, and very few more. The other two changes run through all three conjugations — cerrar, entender and preferir; contar, volver and dormir.

Some of these are met mostly in the third person: cuesta diez euros, llueve, nieva.

In popular speech in several countries a few of them are said without the change — apreta for aprieta, neva for nieva. The grammar records the habit and notes that it has not settled into careful Spanish, and the academies' usage dictionary marks apreto as incorrect: write aprieta and nieva.

Irregular yo forms: hago, salgo, conozco, sé

A second family is irregular in one form only. A g appears in the yo form of hacer, poner, salir and valer (hago, pongo, salgo, valgo), and an ig in traer and caer (traigo, caigo). Conocer and the verbs in -ecer take zc — conozco, parezco, agradezco, ofrezco — and so do the verbs in -ducir: conduzco, traduzco. Saber gives sé, caber quepo, dar doy and ver veo.

Sé is written with its accent, which keeps it apart from the pronoun se. The academies list sabo and sepo among the forms to avoid.

The yo form matters twice, because the present subjunctive is built on it: hago gives haga, conozco gives conozca, salgo gives salga. Learn the yo form and the subjunctive comes with it.

Verbs that do both: tengo, tienes; digo, dices

Tener and venir are e → ie verbs with a g in the yo form: tengo, tienes; vengo, vienes. Decir is e → i with the same g: digo, dices. Their compounds follow them — mantener, obtener and detener (mantengo, mantienes), prevenir (prevengo, previenes), predecir and contradecir (predigo, predices).

Seguir and elegir add a spelling change to e → i. Seguir drops its silent u before o — sigo, not siguo — and so does conseguir (consigo). Elegir, recoger and dirigir write j before o to keep the sound: elijo, recojo, dirijo; before e and i the g stays — elige, never elije.

Oír puts a y between vowels — oigo, oyes, oye, oyen, but oímos and oís — and the verbs in -uir do the same: construyo, construyes, construye, construyen, but construimos.

Three verbs follow no pattern at all and are simply learned: ser (soy, eres, es, somos, sois, son), ir (voy, vas, va, vamos, vais, van) and haber (he, has, ha, hemos, habéis, han). Estar is regular except for estoy and its stress: estás, está, están.

With vos, the stem does not change

In Argentina, Paraguay and Uruguay, where vos is the everyday form at every social level, the vos form is stressed on its ending — pensás, podés, pedís, tenés — so the stem keeps its vowel. The dictionary's tables print both side by side: piensas / pensás, puedes / podés, pides / pedís, tienes / tenés. It is the rule at work, not an exception to it: no stress on the stem, no change.

Do stem-changing verbs change in other tenses?

The same vowels change in the present subjunctive (piense, pueda, pida) and in the tú command (piensa, vuelve, pide). The -ir verbs go one step further: in the gerund and in two preterite forms the vowel closes — sintiendo, sintió, sintieron; durmiendo, durmió, durmieron; pidiendo, pidió, pidieron. The -ar and -er verbs have no change there: pensando, pensó; volviendo, volvió.

The imperfect never changes — pensaba, podía, pedía. Preterite vs imperfect is the choice between those two past tenses, and the future tense is where twelve of these verbs shorten instead: tendré, podré, diré.

Why do English speakers get stem-changing verbs wrong?

English verbs barely change — I think, you think, we think — so a learner builds the Spanish form straight from the infinitive: yo penso, yo podo, yo sabo. Once the change is learned, the slip runs the other way: nosotros piensamos, nosotros puedemos, with the change carried into the two forms that never take it.

It is also the mistake our learners make most often. Nivelo grades every conversation turn and writing task against the grammar it uses. Across 47 learners and 2,843 present-tense forms (recounted 24 September 2026), 22% were wrong — 638 slips, more than a quarter of every mistake we have tagged. By level: A1 31%, A2 26%, B1 22%, B2 16%, C1 21%. The count covers every present-tense slip — a stem that should have changed, an irregular yo form, an ending that does not match its subject — so it measures the tense, not this chart alone. It is a count of our own learners, not a study.

What comes after stem-changing verbs?

The present tense has the rest of the tense — the regular endings, the five verbs that are irregular everywhere and the other yo forms: hago, conozco, sé. The future tense is the next set of forms: one set of endings, and twelve verbs that shorten first. The irregular preterite is where tener, poder and decir change again: tuve, pude, dije. The present subjunctive is built on the yo forms on this page — tengo gives tenga, pido gives pida. Spanish commands keep the change in the tú form — piensa, vuelve, pide — and six of the verbs on this page have a short one: di, haz, pon, sal, ten, ven. Reflexive verbs keep the change too: me acuesto, me siento, me visto. Pedir vs preguntar and jugar, tocar or poner each turn on one of these verbs, and ser vs estar on the two most irregular of all. The free Spanish level test places you on the A1–C2 scale in five minutes; what A2 Spanish means shows where the present tense sits among the things an A2 learner is still building.