eternity vs beingness

eternity and beingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
eternity	Yes	No	No	No
beingness	Yes	No	No	No

As nouns, beingness is a hypernym of eternity; that is, beingness is a word with a broader meaning than eternity:

eternity: a state of eternal existence believed in some religions to characterize the afterlife
beingness: the state or fact of existing

Other hypernyms of eternity include being, existence, face of the earth.

eternity (noun)	beingness (noun)
a state of eternal existence believed in some religions to characterize the afterlife	the state or fact of existing
time without end
a seemingly endless time interval (waiting)