the unending future: time stretching ahead with no stopping point, so most often translated forever
This little word names time that runs forward and never stops. It points to what lies ahead, the open future with no horizon, which is why English Bibles almost always render it forever or for all time to come. It is closely tied to its more common partner olam, the word for the far horizon of time in either direction, and the two are often stacked together for emphasis in the phrase forever and ever.
Most of the time the word works like an adverb pinned onto a verb: a king reigns forever, a truth stands forever, an enemy is wiped out forever. A favorite poetic form doubles it back on itself, for ever and ever, to press the point that the duration truly has no end.
A smaller group of passages lets the word stand more on its own as a name for endless duration itself, and there it brushes up against the eternity of God. When Isaiah speaks of the One who inhabits eternity, or when a promised child is called Father of eternity, the word is no longer just measuring how long something lasts; it is naming the timeless reality that belongs to God. The two uses are the same word seen from two angles: forever as a stretch of time, and eternity as the realm God owns.
The one caution is not to load the word with a philosopher's idea of timelessness. In its world it means duration that does not quit, time without a finish line, rather than the absence of time altogether.