In English, infinitive verbs are preceded by the word to, as in to speak, to read, or to write.
In Spanish, infinitives are only one word and end in either -ar, -er, or -ir, as in hablar , leer , and escribir .
Verb Stems
Many verb tenses use a form of the infinitive as the stem to which verb conjugation endings are attached. In general, for regular verbs, you simply need to remove the infinitive ending (-ar, -er, or -ir) to find the stem, and then you can the add specific endings needed to give tense/subject information.
-ar Verbs
Verbs that end in-ar are more common than -er and -ir verbs. There are also fewer irregular -ar verbs than -er or -ir verbs. Here are some examples of common -ar infinitives and their stems.
Infinitive Definition Stem
buscar
to look for busc-
cantar
to sing cant-
comprar
to buy compr-
escuchar
to listen to escuch-
extrañar
to miss/to yearn for extrañ-
hablar
to speak habl-
llamar
to call llam-
llenar
to fill llen-
llevar
to carry llev-
mirar
to watch mir-
visitar
to visit visit-
-er Verbs
Verbs that end in -er are the second-largest group of infinitives in Spanish. Here are some examples of common -er infinitives and their stems.
Infinitive Definition Stem
beber
to drink beb-
comer
to eat com-
comprender
to understand comprend-
correr
to run corr-
creer
to believe cre-
deber
to owe deb-
leer
to read le-
meter
to put into met-
romper
to break romp-
vender
to sell vend-
-ir Verbs
Verbs that end in -ir are the smallest group of Spanish infinitives. Here are some examples of common -ir infinitives and their stems.
Infinitive Definition Stem
abrir
to open abr-
asistir
to attend asist-
cubrir
to cover cubr-
escribir
to write escrib-
incluir
to include inclu-
pedir
to order ped-
permitir
to allow permit-
recibir
to receive recib-
servir
to serve serv-
vivir
to live viv-