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CEFR A1-A2

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Spanish Stem-Changing Verbs

Stem-changing verbs are usually taught as an irregularity, which is misleading. The endings are perfectly regular. What changes is the vowel inside the stem, and it changes for a reason: Spanish will not leave a stressed e or o alone in these verbs, so it breaks the vowel into a diphthong.

Once you see that the change is driven by stress, the whole pattern stops needing memorisation form by form.

The four patterns

PatternExample verbyo formMeaning
e > ieto want
o > ueto be able
e > ito ask for
u > ueto play

u > ue has exactly one member, . It is listed as a pattern because it behaves identically, not because there is a group to learn.

The boot

Write the six present-tense forms in a column and the changing forms make a boot shape, because the two that do not change sit together in the middle:

(o > ue)

PersonFormChanges?
yopuedoyes
puedesyes
/ / puedeyes
podemosno
podéisno
/ / puedenyes

The boot is a mnemonic, but the reason underneath it is real. Stress falls on the stem in four of the six forms, and on the ending in the other two. stresses the -- of the ending; the stem o is unstressed and stays put. Every form that stresses the stem changes it.

If you remember the reason, you never need the picture.

e > ie, the biggest group

VerbMeaningyo form
to want
to think
to begin
to closecierro
to understand
to prefer
to lose
to feel
  • . (I want a coffee.)
  • ¿A ? (What time does the film start?)
  • No . (I do not understand.) - the most useful sentence on this page

o > ue

VerbMeaningyo form
to be able
to sleep
to return
to find
to cost
to remember
to die
  • ¿ ayudarme? (Can you help me?)
  • ¿ ? (How much does it cost?) - costar is nearly always third person, so you mostly meet it as cuesta and cuestan
  • . (I sleep badly.)

e > i

This pattern is confined to - verbs, and there are no exceptions to that.

VerbMeaningyo form
to ask for
to servesirvo
to repeatrepito
to follow, to continue
to get dressedme
to say

is stem-changing and separately irregular in the yo form - , not dico. drops the u for spelling reasons in the yo form: .

  • . (I ask for the bill.)
  • ¿ , favor? (Can you repeat that, please?)

pedir vs preferir: the trap

Both have an e in the stem and both are - verbs, and they change differently:

  • goes e > i: pido
  • goes e > ie: prefiero

There is no rule that predicts which. Dictionaries and word lists mark it, usually as (i) and (ie), and that marking is worth reading rather than skipping.

What stem changes do not affect

  • The endings. Every form takes the ordinary -ar, -er or -ir ending for its person.
  • The infinitive. You still say , never quiero duermo. The second verb stays in the infinitive.
  • The imperfect. Podía, quería, pedía are all regular with no stem change at all.
  • Most of the preterite. The -ar and -er stem-changers are regular in the preterite: , . The -ir stem-changers do change, but only in the third person: , .

That last point is the one worth holding onto: stem changes are a present-tense phenomenon, with a small third-person echo in the -ir verbs' preterite.

Common mistakes English speakers make

The first is changing and : puedemos, quieremos. These are the two forms that never change, and getting them wrong is the clearest marker of a learner who has memorised the boot picture without the reason behind it.

The second is carrying the change into the infinitive: quiero duermo for "I want to sleep". It is .

The third is assuming the pattern from the infinitive. Comer and poder look structurally identical; only poder changes. There is no shortcut here, only exposure.

The fourth is carrying the change into the imperfect: quiería. The imperfect is regular, so it is .

See also

Practise: test yourself

Pick the right one

0/6

Choose the correct present-tense form.

  1. Yo ir al cine. (poder)

  2. Nosotros ir al cine. (poder)

  3. Ella un café. (querer)

  4. Vosotros un café. (querer)

  5. Ellos la cuenta. (pedir)

  6. Yo al fútbol. (jugar)

Fill in the blank

0/6

Fill the gap with the correct present-tense form. Watch which forms sit outside the boot.

  1. Yo a las siete. (empezar, e>ie) (stressed stem, so the vowel changes)

  2. Nosotros a las siete. (empezar) (nosotros never changes)

  3. Tú en Madrid. (dormir, o>ue) (stressed stem)

  4. Vosotros en Madrid. (dormir) (vosotros never changes)

  5. Él la verdad. (decir, e>i) (e>i, and decir is irregular in the yo form)

  6. Ellas la puerta. (cerrar, e>ie) (stressed stem)

Matching

0/4

Match each verb to its stem-change pattern.

Translation drill

0/4

Translate into Spanish.

  1. I want to sleep.

  2. We want to sleep.

  3. The film starts at eight.

  4. They ask for the bill.

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Frequently asked questions

What is a stem-changing verb in Spanish?
A verb whose stem vowel changes in the present tense when the stress falls on that vowel, while the endings stay completely regular. Poder (to be able) keeps regular -er endings but its o becomes ue under stress: puedo, puedes, puede, podemos, podéis, pueden. The change is driven by stress, which is why nosotros and vosotros are the two forms that never change - in those the stress moves onto the ending instead of the stem.
Why do nosotros and vosotros not change?
Because the stem change happens only when the stem vowel is stressed, and in the nosotros and vosotros forms the stress moves onto the ending. Podemos and podéis stress the -e- of the ending, so the stem o is unstressed and stays as it is. Every other form stresses the stem, so every other form changes. This is what produces the boot shape when you write the six forms out in a column.
How do I know if a verb is stem-changing?
You cannot tell from the infinitive - poder and comer look identical in structure and only one changes. Stem changes have to be learned per verb, which is why dictionaries and word lists mark them, usually as poder (ue) or pedir (i). The good news is that the group is small and front-loaded with very common verbs, so ordinary exposure teaches most of them within a few months.