1. Present Tense Stem-changing Verbs
o-ue
e-ie
e-i
u-ue

2. Remember, there are three types of infinitives: -ar, -er, -ir
Remember, there are three types of infinitives: -ar, -er, -ir. Infinitives are made up of two parts: the ending and the stem. In the following examples, the stem is underlined and the ending is in bold.
hablar comer vivir

3. Endings on Regular Verbs
With regular verbs, the stem stays the same, and the ending changes as they are conjugated.
Hablo, hablas, hablas, hablamos, hablan
Como, comes, come, comemos, comen
Vivo, vives, vive, vivimos, viven

4. The Three Stem-changing Verb Groups
With some verbs, the stem also changes when you conjugate them. In the present tense, there are four groups of stem-changing verbs:
o:ue e:ie e:i
u-ue

5. o-ue
With the first group of stem-changing verbs, the letter o in the stem changes to ue in all forms except the nosotros.
contar cuento cuentas cuenta contamos cuentan

6. Here's another o:ue stem changing verb
Here's another o:ue stem changing verb. Compare it to the regular verb comer. Notice that the endings are the same for regular verbs and stem-changing verbs.
mover (o:ue) comer (regular -er verb) muevo como mueves comes mueve come movemos comemos mueven comen

7. o-ue
Here's another o:ue stem-changing verb. Notice how the stem doesn't change in the nosotros.
dormir (o:ue) duermo duermes duerme dormimos duermen

8. e-ie
With the second group of stem-changing verbs, the letter e in the stem changes to ie in all forms except the nosotros.
cerrar cierro cierras cierra cerramos cierran

9. Here's another e:ie stem changing verb
Here's another e:ie stem changing verb. Compare it to the regular verb comer. Notice that the endings are the same for regular verbs and stem-changing verbs
entender (e:ie)
comer (regular -er verb) entiendo como entiendes comes entiende come entendemos comemos entienden comen

10. e-ie
Here's another e:ie stem-changing verb. Notice how the stem doesn't change in the nosotros.
mentir (e:ie) miento mientes miente mentimos mienten

11. e-i
With the third group of stem-changing verbs, the letter e in the stem changes to i in all forms except the nosotros.
servir
sirvo
sirves
sirve
servimos
sirven

12. e-i
Here's another e-i stem-changing verb. Notice how the stem doesn't change in the nosotros.
pedir (e-i) pido
pides
pide
pedimos
piden

13. u-ue
Here's a u-ue stem-changing verb. Notice how the stem doesn't change in the nosotros.
Jugar: (u-ue) juego
juegas
juega
jugamos
juegan