eonian vs eternal

eonian and eternal both are adjectives.

Word	Noun	Adjective	Verb	Adverb
eonian	No	Yes	No	No
eternal	No	Yes	No	No

As adjectives, eonian and eternal are synonyms defined as:

Other synonyms of eonian include aeonian, ageless, everlasting, perpetual, unceasing, unending.

eonian (adjective)	eternal (adjective)
of or relating to a geological eon (longer than an era)	tiresomely long; seemingly without end
continuing forever or indefinitely	continuing forever or indefinitely