GK, it depends on the context. In language translation, context is everything. Thus, for example, "seize the moment" in Latin is "seize the day." Give you another example: years ago, a German VIP said to some American (reporter?), "You are high on wire!" He was literally translating the German expression "Sie sind hoch auf Draht," which in English would be "you're really on the ball!" On the other hand, an American who was a wooden literalist might take THAT expression and make it into "Sie sind wirklich auf dem Ball" which makes zero sense in German.
in a moment = statim or confestim
at the moment = hoc tempore
for the moment = in praesens
of great moment = magni momenti
Hope one of those is useful!