Verbs with Stem Change
Before we start seeing verbs that have stem change, let us talk about the verb stem first. A verb stem is a part of the verb where suffix can be attached. So, if I take “tener” as an example, since the ending is -ER, ten- should be the stem for “tener”.
Since we know what the stem is, now we talk about how they change. It is always a vowel that changes in a stem, and there are 3 types of verbs that have stem change.
o →ue
dormir to sleep
acostarse to go to bed
volver to return
jugar to play
almorzar to eat lunch
| dormir | Singular | Plural |
| 1st Person | duermo | dormimos |
| 2nd Person | duermes | dormís |
| 3rd Person | duerme | duermen |
e→ie
pensar to think
*tener to have
entender to understand
preferir to prefer
sentirse to feel
venir to come
querer to want
despertarse to wake up
| pensar | Singular | Plural |
| 1st Person | pienso | pensamos |
| 2nd Person | piensas | pensáis |
| 3rd Person | piensa | piensan |
e→i
pedir to ask for
vestirse to get dressed
| pedir | Singular | Plural |
| 1st Person | pido | pedimos |
| 2nd Person | pides | pedís |
| 3rd Person | pide | piden |
As you may have noticed, stem in nosotros and vosotros forms stays the same as their infinitive form of the verb. And, I personally remembered this visually imagining an L on the conjugation table.
| volver | Singular | Plural |
| 1st Person | vuelvo | volvimos |
| 2nd Person | vuelves | volvís |
| 3rd Person | vuelve | vuelven |
*Tener in yo form is completely irregular. “Yo tengo.”