Lesson 11: Stem-changing verbs (verbos con cambio en el radical)

Part 1: The big idea — the "boot" (la bota)

Some verbs break the stem vowel in 4 of the 6 present-tense forms: yo, tú, él, ellos. The nosotros and vosotros forms keep the infinitive stem untouched. Stacked vertically, the four affected cells form the shape of a boot (or "shoe"):

   yo        │ CHANGES   │  ┐
   tú        │ CHANGES   │  │  upper part of the boot
   él/ella   │ CHANGES   │  ┘
   nosotros  │ unchanged │  ← sole of the boot
   vosotros  │ unchanged │  ← sole of the boot
   ellos     │ CHANGES   │  ← heel of the boot

Why? In nosotros / vosotros the stress falls on the ending (que-RE-mos, que-RÉIS) — the stem vowel is unstressed and stays calm. In the other four forms the stress lands on the stem — and the vowel "breaks".

One-line rule: stressed stem vowel → it changes. Unstressed → it doesn't.

The pattern is unpredictable from the infinitive alone — you can't look at querer vs correr (regular, to run) and tell which one breaks. You have to memorize which verbs are stem-changers. But once a verb is in the club, the change itself is 100% systematic: just apply the boot.

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Part 2: Type e → ie

The most populous group. A stressed stem e turns into ie.

Querer (to want; to love a person) — the model verb for e→ie

Person	Form	Stem
yo	quiero	quier-
tú	quieres	quier-
él / ella / usted	quiere	quier-
nosotros	queremos	quer- ← unchanged
vosotros	queréis	quer- ← unchanged
ellos / ellas / ustedes	quieren	quier-

Notice: the endings (-o, -es, -e, -emos, -éis, -en) are exactly the regular -ER endings from Lesson 7. Only the middle vowel did the gymnastics.

Other e→ie verbs

Infinitive	English	yo-form	nosotros
pensar	to think	pienso	pensamos
empezar	to begin, to start	empiezo	empezamos
cerrar	to close	cierro	cerramos
entender	to understand	entiendo	entendemos
perder	to lose	pierdo	perdemos
preferir	to prefer	prefiero	preferimos
sentir	to feel	siento	sentimos
comenzar	to begin (synonym of empezar)	comienzo	comenzamos

Useful combos: pensar en (to think about): Pienso en ti. | empezar a + inf. (to start doing): Empiezo a entender.

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Part 3: Type o → ue

A stressed stem o turns into ue.

Poder (to be able to, can) — the model verb for o→ue

Person	Form
yo	puedo
tú	puedes
él / ella / usted	puede
nosotros	podemos
vosotros	podéis
ellos / ellas / ustedes	pueden

Poder is followed by an infinitive: ¿Puedes ayudarme? — Can you help me? No puedo dormir. — I can't sleep.

Other o→ue verbs

Infinitive	English	yo-form	nosotros
dormir	to sleep	duermo	dormimos
volver	to come back, to return	vuelvo	volvemos
encontrar	to find, to meet	encuentro	encontramos
contar	to count; to tell (a story)	cuento	contamos
recordar	to remember	recuerdo	recordamos
costar	to cost (usually 3rd person)	cuesta	cuestan
soñar (con)	to dream (of)	sueño	soñamos
almorzar	to have lunch	almuerzo	almorzamos

Useful combo: volver a + inf. — to do something again: Vuelvo a leer el libro. — I'm reading the book again.

The odd one out: jugar (u → ue)

A single Spanish verb does u → ue: jugar (to play). Same boot pattern, different starting vowel.

Person	Form
yo	juego
tú	juegas
él / ella / usted	juega
nosotros	jugamos
vosotros	jugáis
ellos / ellas / ustedes	juegan

Useful collocation: jugar al fútbol, jugar al tenis — to play (a + el = al) a sport.

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Part 4: Type e → i (only -IR verbs!)

A stressed stem e turns into i. This group is a closed club: only -IR verbs. If a verb ends in -AR or -ER, it will NEVER follow this pattern.

Pedir (to ask for, to order) — the model verb for e→i

Person	Form
yo	pido
tú	pides
él / ella / usted	pide
nosotros	pedimos
vosotros	pedís
ellos / ellas / ustedes	piden

Other e→i verbs

Infinitive	English	yo-form	nosotros
servir	to serve	sirvo	servimos
repetir	to repeat	repito	repetimos
seguir	to follow; to continue	sigo / sigues / sigue…	seguimos
conseguir	to obtain, to get	consigo	conseguimos

Spelling trap with seguir: the yo-form drops the u: sigo (not siguo). Reason: gu+o would read "gwo", but the verb is supposed to say "go" — so the u disappears. Same trick with conseguir → consigo.

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Part 5: Pedir vs preguntar — two "to ask"s

English has ask for (a thing) and ask (a question). Spanish keeps these as two completely different verbs:

Verb	What it means	Example
preguntar	to ask a question (request information)	Te pregunto: ¿dónde vives? — I'm asking you: where do you live?
pedir	to ask for / request (a thing or a favor)	Te pido un favor. — I'm asking you for a favor. Pido un café. — I'll have / I'm ordering a coffee.

Memory hack: preguntar = ask for information, pedir = ask for a thing or an action. preguntar is a regular -AR verb — no stem change: pregunto, preguntas, pregunta, preguntamos, preguntáis, preguntan. pedir is e→i: pido, pides, pide, pedimos, pedís, piden.

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Part 6: How do you know if a verb is a stem-changer?

You don't — until you've met it. Two clues help: (1) dictionaries mark it as querer (ie), poder (ue), pedir (i); (2) word families behave alike — if pensar (ie), then empezar, cerrar are also (ie); if poder (ue), then volver, dormir, encontrar are also (ue).

The shortcut: memorize the yo-form. From it you can reconstruct the rest of the boot by changing the ending; the sole (nosotros/vosotros) just goes back to the infinitive stem.

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Useful nouns to go with the verbs

Spanish	English
la pregunta	question (f.)
la respuesta	answer (f.)
el favor	favor (m.)
el sueño	dream; sleepiness (m.)
la cuenta	bill (in a café) (f.)

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