Chapter 23 · A2
Present Tense: Stem-Changing & Irregular Verbs
Might help first: Ch. 20 — Verb Conjugation System: Overview & Regular Verbs, Ch. 22 — Present Tense: Regular -AR/-ER/-IR Verbs (a suggestion, never a requirement)
Chapter 22 covered the -ar/-er/-ir pattern that most Spanish verbs follow without exception. This chapter covers the verbs that don’t — and there are a lot of them, including some of the most common verbs in the language: querer, poder, tener, ir, ser, decir. You reach for these constantly, so it’s worth knowing up front that native speakers don’t experience them as a random pile of exceptions memorized one by one. They cluster into a small number of recognizable families, and once you can name which family a new verb belongs to, you already know how it conjugates. That’s the real skill this chapter builds — not memorizing hundreds of individual verbs, but recognizing which of a handful of patterns a verb falls into.
Core Pattern: The E → IE Stem Change
The boot shape: yo, tú, él/ella/usted, ellos/ellas/ustedes
A2The single largest family of present-tense irregulars is the stem-changing (or “boot”) verbs. In four of the six forms — yo, tú, él/ella/usted, and ellos/ellas/ustedes — the last vowel of the stem shifts, while nosotros and vosotros keep the stem exactly as it appears in the infinitive. Drawing a line around the four changed forms in a two-column grid traces a boot, or shoe, shape — which is where the traditional name comes from:
Siempre pierdo las llaves.
I always lose my keys.
Nosotros nunca perdemos la paciencia.
We never lose patience.
More e→ie verbs
A2The same pattern governs a long list of common verbs across all three conjugations: empezar, pensar, cerrar, comenzar (-ar); entender, querer (-er); preferir, sentir, mentir (-ir).
¿En qué piensas?
What are you thinking about?
Prefiero el té al café.
I prefer tea to coffee.
Building Out: The Other Stem-Change Families
The same boot-shaped logic — stressed stem vowel changes, nosotros/vosotros don’t — extends to two more vowel patterns. Once e→ie is second nature, these are the same skill applied to a different starting vowel.
O → UE
A2Duermo ocho horas cada noche.
I sleep eight hours every night.
¿Puedes ayudarme?
Can you help me?
Other common o→ue verbs: poder, volver, contar, encontrar, recordar, costar, morir.
E → I (only in -IR verbs)
A2Siempre pido la misma tapa.
I always order the same tapa.
Other e→i verbs: servir, repetir, vestir(se), seguir, elegir. This third pattern is narrower than the other two in one useful way: it only ever happens in -ir verbs. There’s no -ar or -er verb anywhere in Spanish that changes e→i — if you see that change, you already know the verb ends in -ir.
Nuance, Exceptions & Contrast
Yo-irregulars: g-insertion, sometimes teamed up with a stem change
A2A separate family of verbs adds a g to the yo form only — a spelling/sound irregularity, not a stem-vowel one. Tener is the clearest example, and it happens to combine both irregularities at once: g-insertion in yo, plus the e→ie stem change everywhere else in the boot:
Tengo dos hermanos.
I have two siblings.
¿Tienes hambre?
Are you hungry?
All four boot cells here differ from the nosotros/vosotros baseline (tenemos, tenéis), so the outline still traces the familiar four-cell boot — but for two genuinely different reasons stacked together: tengo breaks the pattern by adding a consonant, while tienes/tiene/tienen break it with the ordinary e→ie vowel shift. Venir (vengo, vienes, viene, venimos, venís, vienen) and decir (digo, dices, dice, decimos, decís, dicen — g-insertion plus e→i this time) work the same combined way.
Pure g-insertion: only the yo form changes
A2Many more common verbs add the same g in yo but are otherwise completely regular — no stem change anywhere else in the paradigm:
Hago la cena todos los martes.
I make dinner every Tuesday.
Él hace ejercicio por la mañana.
He exercises in the morning.
Here, only one of the four “boot” cells is actually irregular — haces, hace, and hacen follow the plain regular pattern from Chapter 22. The irregularity traces a single cell around yo, not a four-cell boot. It’s still a genuine, worth-learning irregularity — just not boot-shaped, since three of the four boot cells behave normally. Salir (salgo, sales, sale, salimos, salís, salen), poner (pongo, pones…), traer (traigo, traes…), and caer (caigo, caes…) all work the same single-cell way.
The -zco family: conocer, conducir, and relatives
B1A related but distinct single-cell pattern: verbs ending in a vowel + -cer or -cir insert a z before the c in the yo form only, to keep the /θ/ sound consistent before the o ending.
| Infinitive | yo form |
|---|---|
| conocer (to know/be familiar with) | conozco |
| conducir (to drive) | conduzco |
| traducir (to translate) | traduzco |
| parecer (to seem) | parezco |
| ofrecer (to offer) | ofrezco |
| agradecer (to thank) | agradezco |
Conozco a tu hermana.
I know your sister.
Orthographic-only changes: preserving the sound, not changing it
B1A final small family isn’t really an irregularity at all in the spoken language — only in spelling. Spanish g and c change pronunciation depending on the vowel that follows them, so when a verb’s stem ends in -ger, -gir, or -cer/-cir with a hard consonant sound, the yo form has to swap the letter to keep the sound the same before the -o ending:
| Infinitive | yo form | Why |
|---|---|---|
| coger (to take/grab) | cojo | g before o would sound hard; j keeps the /x/ sound |
| escoger (to choose) | escojo | same |
| proteger (to protect) | protejo | same |
| dirigir (to direct) | dirijo | same g→j logic before o |
| exigir (to demand) | exijo | same |
| elegir (to choose/elect) | elijo | g→j, and e→i stem change (eliges, elige, eligen) |
| vencer (to defeat) | venzo | c before o would lose its /θ/ sound; z keeps it |
| convencer (to convince) | convenzo | same |
| seguir (to follow/continue) | sigo | gu→g before o, and e→i stem change (sigues, sigue, siguen) |
Fully irregular verbs: ser, estar, ir, haber
A1A handful of the most essential verbs in Spanish don’t fit any family above — their forms come from entirely different, fused-together historical roots, a pattern linguists call suppletion. Ir is the clearest case:
Voy al mercado los sábados.
I go to the market on Saturdays.
Notice there’s no meaningful boot outline to draw here: the boot-table logic works by contrasting the yo/tú/él-ella-usted/ellos-ellas-ustedes forms against a “regular” nosotros/vosotros baseline, but vamos and vais are just as irregular — just as disconnected from a plain infinitive stem “i-” — as the rest of the paradigm. When every cell is irregular, including the ones that normally serve as the baseline, there’s no unaffected shape left to trace a boot around.
Ser, estar, and haber are irregular the same fundamental way, though each keeps slightly more of a recognizable pattern:
| yo | tú | él/ella/usted | nosotros | vosotros | ellos/ellas/ustedes | |
|---|---|---|---|---|---|---|
| ser | soy | eres | es | somos | sois | son |
| estar | estoy | estás | está | estamos | estáis | están |
| haber | he | has | ha | hemos | habéis | han |
A common learner error: overgeneralizing the boot
B1Once the e→ie/o→ue/e→i pattern clicks, a predictable new mistake shows up: extending the stem change into nosotros or vosotros, where it never belongs.
Nosotros pensamos ir al cine, no nosotros piensamos ir al cine.
We're planning to go to the movies.
The fix is the same stress logic from the start of this chapter: nosotros and vosotros always stress the ending, never the stem, so the stem always stays in its plain infinitive form — no exceptions among any of the three vowel families.
Bringing It Together
Cuando tengo hambre, pido algo de comer; si no puedo decidir, prefiero lo que pide mi hermano. Nosotros nunca perdemos tiempo pensando demasiado — simplemente vamos al restaurante y ya.
When I'm hungry, I order something to eat; if I can't decide, I prefer whatever my brother orders. We never waste time overthinking it — we just go to the restaurant and that's that.
Faced with a new verb, work through it in this order: first, is it one of the handful of fully irregular verbs (ser, estar, ir, haber, and a few others you’ll simply memorize)? If not, does the stressed stem vowel show e or o, and is it a verb you recognize as a stem-changer? If not, check the yo form specifically — does it need a g, a z, or a spelling swap to keep its sound? If none of that applies, it’s simply regular, and Chapter 22’s pattern covers it completely.
Where to Go Next
- Chapter 20, Verb Conjugation System: Overview & Regular Verbs and Chapter 22, Present Tense: Regular Verbs — the regular baseline every irregularity in this chapter is measured against.
- Chapter 21, Ser vs. Estar — the full decision framework behind the two verbs only briefly re-tabled here.
- Chapter 24, Gustar & Verbs Like It — gustar is grammatically regular in form, but its sentence structure is its own kind of irregular worth learning right after this chapter.
- Chapter 25, Present Progressive — several verbs in this chapter’s e→i and o→ue families (pedir, dormir, seguir) show a related, but not identical, vowel change in their gerunds.
- Chapter 27, El Pretérito Indefinido: Irregular Verbs — many of this chapter’s irregular stems (tuve, hice, dije…) reappear reshaped in the preterite.
- Chapter 36, Commands — several of this chapter’s yo-irregular forms (tengo, hago, salgo, pongo, digo, vengo) resurface as the base for irregular command forms.
- Chapter 37, El Presente de Subjuntivo: Formation — the subjunctive stem for most irregular verbs is built directly from the irregular yo form taught in this chapter.
Ready to practice?
12 exercises · multiple-choice, fill-blank, conjugation-grid…