What exactly is the "economy"?

The most basic question ever, but I have always been confused by that, and for good reasons. <br><br>It is too vague, and yet, everyone seems to know what it is without knowing how to exactly define it in a concrete way. The level of abstraction and vagueness is staggering. The size of the economy seems to be the most important metric for measuring a nation's wealth and power.<br><br>Am I correct in feeling that the "economy" is an abstract construct that cannot be directly measured or seen, but what can be measured is the money supply and flow within a society? It is as if "the economy" is a metaphorical entity that requires certain preconditions to function according to basic laws of economics. It is not a direct entity, but a hegemonic entity that can be directly measured only indirectly. GDP is too vague, as it includes even the money raised from selling narcotics, amongst other things.