lasting on and on without stopping: forever, perpetually, to the very end
This is the everyday meaning of the word, and almost every time it appears it is part of a stock phrase that works like the English adverb "forever" or "perpetually." Its core idea is duration that does not let up. Translators reach for different English words depending on the verse, which is why one Hebrew word can show up as forever, always, continually, perpetually, to the end, or utterly.
The spread of those renderings is not three unrelated ideas but one idea seen from different angles. When the duration is good, it lands as "forever" (joys at God's right hand forevermore). When a sufferer feels it as God's silence dragging on, it becomes the anguished "How long, will it be forever?" of the laments. And when something is wiped out so finally that it can never come back, the same unbroken duration reads as "utterly" or "to the very end."
Much of its weight in the Bible is theological precisely because it is so often negated: God does not stay angry forever, does not forget the needy forever, will not cast off forever. The word names the limitless stretch that God, in mercy, refuses to fill with judgment.