The Greek word, aionios (G166), is the adjective of the noun, aion (G165). It represents a time span of an indefinite duration. This adjective must be defined in context or comparing the text with other Scriptures that speak about the same subject matter and are more definitive relative to time duration. For example:
In hope of eternal (G166) life, which God, that cannot lie, promised before the world (G166) began; [Titus 1:2 KJV]
in hope of eternal (G166) life, which God, who cannot lie, promised before times eternal (G166); [Titus 1:2 ASV]
in hope of eternal (G166) life, which God, who does not lie, promised before the ages (G166) began. [Titus 1:2 NET.]
If you were able to read Greek you would know from Titus 1:2 that aionios life was promised before aionios times began. The three translations above show with varying degrees of clarity that eternal life was promised **before** eternal times (eternity). What does this mean? It cannot be forced to say eternity has a beginning; this statement or translation doesn’t make sense. If the promise was made at all, it had been promised to a human being, otherwise what would the word promise mean? So, if the promise was made before aionios times began, it would be ludicrous, as I said above, to say this Greek word means eternity or eternal (everlasting or forever). Moreover it is in the plural. How could there be more than one eternity? This is illogical.
The KJV is poorly translated here and probably done so to adapt the text to the traditions of the past. The ASV is even more ridiculous when it speaks of ‘before times eternal’. How can anything be **before** eternity? Does eternity have a beginning? Does God, who is eternal have a beginning? This translation is very poor here. The NET is much better saying eterna life was promised before the ages began, showing not only that the word does not mean eternal but that there can be many.
The word aionios has to do with an indefinite period of time. For example, Philemon 1:15 has Paul sending to Philemon his escaped slave, Onesimus, who under Paul’s ministry had become a Christian. Paul then told Philemon he could now receive him forever (G166). Does Paul mean Onesimus would remain Philemon’s slave in eternity? That would be ridiculous. It could only mean for as long as he or Onesimus were alive—or until Philemon sets him free, which I believe Paul is implying would be the best thing to do. Whatever occurred, aionios could mean only an indefinite period of time. It could be years (until death) or it could mean a short time, if Philemon released his brother in Christ, which tradition says he did.
Another Scriptural example is Jude 1:7 where we find God judged Sodom and Gomorrah for their sins, and they suffered “the vengeance of **eternal** (aionios) fire.” The fire certainly is not burning today, so it cannot be an eternal fire. Neither could it mean that the results are eternal, because Sodom and Gomorrah will be raised one day by God in the Great White Throne Judgment (cp. Matthew 10:15; Revelation 20:11). The word in this context can mean only that the fire completely burned up Sodom and Gomorrah. As long as a remnant of those cities existed, the fire continued to burn. It burned for an indefinite period of time, and when there was no longer fuel (Sodom and Gomorrah) to burn, the fire went out!
What about the noun, aion (G165), does this Greek word mean eternal or eternity? No, it does not! Consider, for example, its use in Hebrews 1:2. There we are told God spoke to us through Christ in these last days, and it was by his Son that God created the ages (G165). The word is in the plural, and, since it would be ridiculous to even consider there being more than one eternity, we conclude the ages (however many there are) were brought into existence through the One who became Jesus. In Colossians 1:26 we find the Gospel has been made manifest to us, but was hid in ages past, which again shows the word cannot mean forever, eternity or everlasting. Ephesians also speaks of **ages** (same word) to come where God intends to show the riches of his grace that he displayed in us through Christ Jesus. How can we not see that it is wrong to translate these words as though they had no ending? How can we not see that by doing so, we are adding the traditions of men to the word of God which we are forbidden to do (Revelation 22:18-19)?
Some might conclude with this understanding that we have shot ourselves in the foot, because, whatever we do with aionios regarding ages past, we must also do to aionios life. How could we translate it ‘eternal’ at the beginning of Titus 1:2 and not at the end of the verse? This is an accurate critique. We must not go beyond what the Scriptures conclude (1Corinthians 4:6). However, it would be accurate to translate aionios into the English word ‘eternal’ (life) at Titus 1:2, because of the context of what we are promised elsewhere. Paul says in 1Corintians 15:53 “this corruptible must put on incorruptibility, and this mortal must put on immortality (G110).” The word here means ‘deathlessness’ or immortality. Speaking of Christ, 1Timothy 6:16 says he alone has immortality, the same word as 1Corinthians 15:53. Finally, in 2Timothy 1:10 Paul speaks of the Gospel, hidden in ages past, brought immortality (same word) to light for us to know and understand.
May God, whose boundless love has given us Christ—in whom we are blessed with every spiritual blessing—guide us to understand the truth of the Gospel, hidden in ages past, but unveiled for us in this present age to know and understand. And, may we glorify and honor him by believing the truth that is in Christ, Jesus. Praise God!