the farthest horizon of time a speaker can see: the remotest past, the unending future, or simply forever, with the direction and the distance set by what is being talked about
At its core this word does not name a fixed amount of time but the farthest edge of time a speaker can imagine, the point where time runs out past where anyone can see. Which direction it faces is supplied by the sentence around it, not by the word itself. Looking back it reaches into a past too old to remember; looking forward it stretches on with no end in view. The same word covers both, which is why it can mean "the ancient days of old" in one verse and "forever" in the next.
How far that horizon reaches depends on what the word is attached to.
- A slave who serves his master for olam serves him as long as he lives.
- A covenant or a rule that stands for olam stands as long as that thing is meant to last, unbreakable within its own sphere.
- The mountains that are olam are primeval, older than memory.
- And when the word is said of God, it stretches to the very limit of what a person could conceive, the horizon beyond all horizons.
The strongest expressions pile the word up or double it, from everlasting to everlasting, forever and ever, to press it as far as language can reach. Most often this heaping is a way of saying for as long as can possibly be imagined rather than a careful claim about timelessness.
In the latest books of the Hebrew Bible a new use begins to appear: the word starts to name an age or era as a thing in itself, the seed of the much later idea of this world and the world to come. In the older writings, though, it remains an open horizon of time rather than a bounded thing or a realm.