Hastings' Dictionary of the Bible (1898)
ETERNAL, ETERNITY. " The difference between them consists in the fact that olam usually means the world in time, although the only place where it is so rendered in our version is Eccl 3:11. But Ps 90:1 is literally "from world to world," Ps 145:13, "kingdom of all worlds," Deut 33:27; "the arms of the world" (English Version, "everlasting arms"). The underlying thought in these passages is that of immense time movements exhibiting God's great work. The Hebrew and Greek words both had plurals, which proves that they did not in themselves denote absolute endlessness.
They are likewise applied to finite things. Gen 17:8; Isa 49:26; Ex 12:14. When they are applied to God and spiritual things they indicate the endless succession of ages, which is the popular and necessary conception of eternity. The idea of absolute eternity is impressed in the Bible by language which implies finality. It is this which renders Matt 25:46 so impressive. The verse sets forth the last act of the great drama of human life, and the rewards and penalties are awarded irreversibly. Here the curtain falls.