Because their stem changes
Why are s/c verbs called s/c verbs?
almorzar
to eat lunch
to begin, to start
empezar
to ask for, to order
pedir
hablar
NOT! No verbs with -a in the stem will stem-change in any conjugation. They might have other conjugations that are weird, but don't s/c.
All the endings stay the same (are regular) in the present tense.
What happens to the verb endings of conjugations for s/c verbs?
to be able to, can, may
poder
to understand
entender
to repeat
repetir
decir in the nosotros form
NOPE - s/c verbs don't s/c change in the nosotros OR vosotros form.
Stem + Infinitive ending
What are the two parts of the infinitive?
costar
to want, to like, to love
querer
to serve
servir
Tener in the yo form
Nope! "Yo tengo __." tienes, tiene, tenemos, tienen
encontrar
sentar
to sit
to dress one's self
vestir
mover (to move)
Stem-changing!
Why are these verbs associated with a boot?
Why ARE these verbs associated with a boot?
morir
sentir
to feel (emotion)
describir
Nope!
"de" is a prefix, and the vowels in prefixes don't ever stem-change. The rest of the stem doesn't have any vowels that s/c.