Money, it seems to me, is rules. Rules about value and obligation. The rules can be enforced or overseen by government or they can be loosely enforced through private self organisation. The opposing arguments about money being from the state or private sources is really a non-argument. They are just different kinds of rules. What we are seeing in the global capital market is the shifting of the rule making away from governments and towards private actors, but both are typically involved. It is just that the balance over the last decade has been skewed towards traders, leaving governments to fix the mess when it all inevitably went wrong.Given that definition-- which I think is profoundly insightful-- the real question is not "what is money," but who made the rules? The folks at NC seem incapable of asking that deeper question.
Anyway, I answer the original question-- what is money-- by considering what money does in a society, while pondering who made the rules that money embodies. Money equals force.