serenity vs tranquillity

serenity and tranquillity both are nouns.

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

As nouns, serenity and tranquillity are synonyms defined as:

Other synonyms of serenity include placidity, quiet, repose, tranquility.

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

Other hypernyms of serenity include quietness, quietude, tranquility.

serenity (noun)	tranquillity (noun)
a disposition free from stress or emotion	a disposition free from stress or emotion
the absence of mental stress or anxiety	a state of peace and quiet
	an untroubled state; free from disturbances