Meanings
mute; dumb (unable to speak)
Der Junge war stumm und schwachsinnig.The boy was mute and imbecile.
silent (not speaking); with verbs or adverbs expressing a grade or temporary state
Was bist du heute so stumm?Why are you so silent today?
non-verbal, not explicitly expressed; silent
ein stummer Vorwurfa silent reproach
Examples
GermanEnglish
Helen Keller war blind, taub und stumm.Helen Keller was blind, deaf and dumb.
Tom wurde stumm.Tom went mute.