silence vs shut up

silence is a noun but shut up is not a noun.

Word	Noun	Adjective	Verb	Adverb
silence	Yes	No	Yes	No
shut up	No	Yes	Yes	No

As verbs, silence and shut up are synonyms defined as:

Other synonyms of silence include hush, hush up, quieten, still.

silence (noun)	shut up (noun)
the absence of sound
a refusal to speak when expected
the trait of keeping things secret
the state of being silent (as when no one is speaking)

silence (adjective)	shut up (adjective)
	closely confined

silence (verb)	shut up (verb)
cause to be quiet or not talk	cause to be quiet or not talk
keep from expression, for example by threats or pressure	refuse to talk or stop talking; fall silent
	place in a place where something cannot be removed or someone cannot escape