Some of the verbs we have introduced previously as irregular are actually stem-changing verbs. This means that there is a small spelling change in the stem of the verb. However, these verbs do follow a pattern:

e > ie

PENSAR (to think)
 

o or u > ue

VOLVER (to return)
 

e > i (ir verbs only)

PEDIR (to ask for)
 

Notice that the nosotros and vosotros forms of the verbs do not have stem changes, whereas the others do.

More Stem-Changing Verbs

e > ie
 

o or u > ue
 

e > i
 

Examples of Present Tense: Stem-Changing Verbs II

• Para estas pastillas no, pero si usted se siente mal mañana, le aconsejo que vea a un médico.
• No lo sé. Comí algo anoche, y no me siento muy bien.