now: the present time, as opposed to the past or the future
This little word marks the present. Most often it simply means "now," the moment of speaking or writing, set against what was true before or what will be true later ("once you were not a people, now you are God's people").
From that plain time sense the word stretches in two directions. It can settle alongside a noun to label something as belonging to the present, as in "this present age" or "the present Jerusalem," marking the here-and-now order of things in contrast to a coming one. And it can lean away from clock time toward logic, where "now" means less "at this moment" and more "as things actually stand" or "so then," the hinge a writer turns on to move from one point to the next.
The three uses are one word seen from different angles, all anchored in the present. Greek often strengthens it with the article ("the now," "from now on," "until now") or pairs it with a particle ("but now," "now therefore"), and the English rendering shifts to match: now, at present, as it is, so then.