#ser# to be; m. being, person
#serio# serious, grave
#servir# to serve, be of use
#seso# brain
#si# if, whether, indeed, why, since; #—— bien# although
#sí# yes, so; himself, herself, itself, one's self, themselves, yourself, yourselves
#siempre# always, ever, for ever
#siete# seven
#silencio# silence
#silla# chair, seat