Español — Stem-changing verbs in the present

In many Spanish verbs the stressed stem vowel changes in the present tense: e→ie (pensar → pienso), o→ue (poder → puedo), e→i (pedir → pido), u→ue (jugar → juego). The endings stay regular.

How it works

✓ Rule

The change happens only where the stem is stressed — in the four "boot" forms yo, tú, él/ella, ellos/ellas. The nosotros and vosotros forms keep the original stem vowel: pensar → pienso, piensas, piensa, pensamos, pensáis, piensan.

Examples

The four change types (yo form vs. nosotros form)
Verb (change)	Meaning	yo / nosotros
pensar (e → ie)	to think	pienso / pensamos
querer (e → ie)	to want	quiero / queremos
poder (o → ue)	to be able to	puedo / podemos
dormir (o → ue)	to sleep	duermo / dormimos
pedir (e → i)	to ask for	pido / pedimos
servir (e → i)	to serve	sirvo / servimos
jugar (u → ue)	to play	juego / jugamos

Good to know

⚠ Note

You can't predict the change from the infinitive alone — tener and comer both have e, yet only tener changes (tengo has other reasons; e→ie shows in tienes, tiene). Learn each verb's pattern, and remember jugar is the only common u→ue verb (juego, but jugamos).