ser, to be.
ser, m., being.
serenidad, f., serenity.
seren-o, -a, serene, calm.
seriedad, f., seriousness.
seri-o, -a, serious.
sermón, m., sermon, reprimand.
sermonari-o, -a, like one delivering a sermon.
serpiente, f., serpent.
serrín, m., sawdust.