eternity vs timeless existence

eternity and timeless existence both are nouns.

Word	Noun	Adjective	Verb	Adverb
eternity	Yes	No	No	No
timeless existence	Yes	No	No	No

As nouns, eternity and timeless existence are synonyms defined as:

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

Other synonyms of eternity include timelessness.

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