by itself, apart from everything else: the idea of one thing standing separate, which gives the common phrase "alone"
At its root this word names a part set off by itself, a single piece kept separate from the rest. By far its most common use is in the phrase that means "alone" or "by oneself", where the word takes a possessive ending so that it reads "in his separateness", "in my separateness", and so on. From there it stretches in two close directions. One is keeping things distinct, counting or handling each piece on its own. The other is the idea of "besides" or "apart from", naming what is left out of a total or added on top of it.
These senses are one thought seen from different angles. Whether the Bible says a person stood alone, that each curtain was joined to itself, or that a number was reached "besides" the women and children, the underlying picture is the same: this one thing held apart from the others. The English word changes, but the Hebrew is making a single point about separateness.
The word almost never stands bare in this meaning. It is normally fixed to the small word for "to" or "from" in front of it, which is why translations render it as a phrase ("by himself", "apart from", "in addition to") rather than a single noun.