Lexical Definition

‎ἀΐδιος‎ aḯdios (ah-id'-ee-os) eternal ^G:A
from ‎ἀεί‎

eternal, everlasting.

• everduring (forward and backward, or forward only)

Abbott-Smith

** ἀΐδιος, -ον (< ἀεί), [in LXX: Wi 7:26, IV Mac 10:15*;]
everlasting (freq. in Inscr.; MM, VGT, s.v.): Ro 1:20, Ju 6.†
SYN.: αἰώνιος, also freq. in Inscr. (Deiss., BS, 363 J. The etymological distinction between the meanings of the two words seems not to be retained in late Greek (v. Thayer, s.v., αἰώνιος; cf. Cremer, 79, 611).

Abbott-Smith References

Liddell-Scott-Jones

ἀΐδιος [ᾱῐδ], ον,

also η, ον, [Refs 5th c.AD+], (ἀεί):— everlasting, eternal, [Refs 8th c.BC+]; οἴκησις, of a tomb, [Refs 5th c.BC+]; ἡ ἀ. οὐσία eternity, [Refs 5th c.BC+]; ἀ. στρατηγία, ἀρχή, βασιλεία, perpetual.., [Refs 4th c.BC+]; τὰ ἀ., opposed to τὰ γενητά and φθαρτά, [Refs]; ἐς ἀΐδιον for ever, [Refs 5th c.BC+]; ad infinitum, [Refs 4th c.BC+]: comparative -ώτερος[Refs 4th c.BC+] —ἀ. is distinct from αἰώνιος as everlasting from timeless, [Refs 6th c.AD+]; but distinct from ἀείζωος as eternal (without beginning or end) from everliving, [Refs]. adverb -ίως[LXX+2nd c.AD+]

_{LSJ Scripture Refs: LXX.Mic.7.18}