timeless existence vs eternity

timeless existence and eternity both are nouns.

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

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

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

Other synonyms of timeless existence include timelessness.

timeless existence (noun)	eternity (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)