silence vs shush

silence is a noun but shush is not a noun.

Word	Noun	Adjective	Verb	Adverb
silence	Yes	No	Yes	No
shush	No	No	Yes	No

As verbs, shush is a hyponym of silence; that is, shush is a word with a more specific, narrower meaning than silence:

Other hyponyms of silence include calm down, lull, shout down, gag, muzzle.

silence (noun)	shush (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 (verb)	shush (verb)
cause to be quiet or not talk	silence (someone) by uttering `shush!'
keep from expression, for example by threats or pressure