Perhaps an example will make things clearer:
In everyday language, "money" has a well-known set of meanings. We say "she makes a lot of money," "he has a lot of money," "it costs a lot of money," "he has no money in his wallet," and so forth--"money" can mean "wealth," "income," "cash on hand,"
In the macroeconomics courses that I teach, when I or the textbook talks of "money"--the "money stock," the "money supply," "demand for money," or any of a number of uses--"money" means one thing and one thing only: wealth held in the form of liquid (i.e., easy to spend) purchasing power.
The macroeconomics textbook meaning of money is *not* the everyday language meaning of money.
Every year I teach undergraduate macroeconomics, some 20% or so of the class doesn't track this sudden shift in the meaning of "money" and become confused. I and the TAs try hard to help them over this hump by warning them that "money" has a special, technical meaning here, that it is probably better to mentally replace "money' with "wealth in a form that is easy to spend" wherever it appeasr in the textbook, and so on.
But in some cases we fail. Perhaps one in twelve final examinations we read gets into big trouble by failing to recall the narrow, technical, macroeconomic definition of money.
Now I claim that Paul Samuelson's, Milton Friedman's, and company's wrenching of the word "money" away from its everyday language definition was a big mistake: something that makes macroeconomics hard to read for a lot of people. They should have written of "liquidity preference" instead of "money demand," and have discussed the supply of "liquid assets" instead of the "supply of money."
Some people would prefer to blame the victims--the people trying to understand who find their task made harder by this sudden shift in meaning. Some people would call for undergraduates confused by the sudden shift in the meaning of "money" to:
--reevaluate their reading habits.
--recognize that thinking outside the boundaries is a complex and
difficult task.
--agree that ambiguity and confusion can be a fruitful source of
new insights.
--abandon the western-intellectual-imperialist hegemonic belief
that clarity and understanding are privileged over other
forms of discourse.
I don't want to blame the victims.
I do want my students to understand, clearly, why it is that when the Federal Reserve sells Treasury bonds unemployment is very likely to rise one year later.
Brad DeLong