Lexical Definition

‎αἰώνιος‎ aiṓnios (ahee-o'-nee-os) eternal ^G:A
from ‎αἰών‎

eternal, for ever, everlasting, world (began).

• perpetual (also used of past time, or past and future as well)

Abbott-Smith

αἰώνιος, -ον (as usual in Attic), also -α, -ον. II Th 2:16, He 9:12; (< αἰών), [in LXX chiefly for עוֹלָם;]
age-long, eternal,
(a) of that which is without either beginning or end: Ro 16:26, He 9:14;
(b) of that which is without beginning: Ro 16:25, II Ti 1:9, Tit 1:2;
(c) of that which is without end (MM, VGT, s.v.): σκηναί, Lk 16:9 οἰκία, II Co 5:1; διαθήκη, He 13:20; εὐαγγέλιον, Re 14:6; παράκλησις, II Th 2:16; λύτρωσις, He 9:12; κληρονομία, ib. 15; κόλασις, Mt 25:46; κρίμα, He 6:2; κρίσις, Mk 3:29; ὄλεθρον, II Th 1:9; πῦρ, Mt 18:8; freq. c. ζωή, q.v.
SYN.: ἀΐδιος, q.v.

Abbott-Smith References

Liddell-Scott-Jones

αἰώνιος, ον,

also α, ον [NT+5th c.BC+]:— lasting for an age (αἰών 11), perpetual, eternal (but distinct from ἀΐδιος, [Refs 5th c.BC+]; κακά, δεινά, [NT+5th c.BC+]; αἰ. διαθήκη, νόμιμον, πρόσταγμα, [LXX+NT+3rd c.AD+]; κόλασις [NT+6th c.AD+]

__2 holding an office or title for life, perpetual, γυμνασίαρχος[Refs]
__3 = Latin saecularis, [Refs 2nd c.AD+]
__4 adverb -ίως eternally, νοῦς ἀκίνητος αἰ. πάντα ὤν[Refs 5th c.AD+]; perpetually, μισεῖν [Refs 5th c.BC+]
__5 αἰώνιον, τό, ={ἀείζωον τὸ μέγα}, Ps.-[Refs 1st c.AD+]

_{LSJ Scripture Refs: Heb.9.12 ☩ Rom.16.26 ☩ LXX.Gen.9.16 ☩ LXX.Exod.27.21 ☩ Matt.25.46 ☩ Matt.25.46 ☩ 2Tim.1.9 ☩ 2Cor.4.18}