eternity vs timelessness

eternity and timelessness both are nouns.

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

As nouns, eternity and timelessness are synonyms defined as:

eternity and timelessness: a state of eternal existence believed in some religions to characterize the afterlife

Other synonyms of eternity include timeless existence.

eternity (noun)	timelessness (noun)
a state of eternal existence believed in some religions to characterize the afterlife	The property of not being restricted to a particular time or date.
time without end	a state of eternal existence believed in some religions to characterize the afterlife
a seemingly endless time interval (waiting)