1: αἰώνιος
(Strong's #166 — Adjective — aionios — ahee-o'-nee-os )

see ETERNAL.

2: ἀΐδιος
(Strong's #126 — Adjective — aidios — ah-id'-ee-os )

denotes "everlasting" (from aei, "ever"), Romans 1:20 , RV, "everlasting," for AV, "eternal;" Jude 1:6 , AV and RV "everlasting." Aionios, should always be translated "eternal" and aidios, "everlasting." "While aionios ... negatives the end either of a space of time or of unmeasured time, and is used chiefly where something future is spoken of, aidios excludes interruption and lays stress upon permanence and unchangeableness" (Cremer).