serenity vs quietness

serenity and quietness both are nouns.

Word	Noun	Adjective	Verb	Adverb
serenity	Yes	No	No	No
quietness	Yes	No	No	No

As nouns, quietness is a hypernym of serenity; that is, quietness is a word with a broader meaning than serenity:

Other hypernyms of serenity include quietude, tranquility, tranquillity.

serenity (noun)	quietness (noun)
a disposition free from stress or emotion	the property of making no sound
the absence of mental stress or anxiety	a state of peace and quiet