金钱是一种在交易中充当交换媒介的好东西。经典地说，货币作为一个帐户单位，一个有价值的存储和一个交换媒介。大多数作者发现前两个是从第三个开始的非必要属性。事实上，其他商品往往比金钱更有价值，因为大多数货币随着时间的推移通过通货膨胀或推翻政府而降价。所以，钱不仅仅是纸上谈兵。它是促进贸易的交换媒介。假设我有一张Wayne Gretzky曲棍球卡，我想交换一双新鞋。没有钱的使用，我必须找到一个人，或者有一双额外的鞋子放弃的人的组合，而恰好正在寻找一个Wayne Gretzky曲棍球卡。很明显，这将是非常困难的。这被称为需要问题的双重巧合：双重巧合是好A的供应商想要好B并且好B的供应商想要好A的情况。重点是货币制度给我们一个更灵活的方法交易比易货交易，它具有想要问题的双重巧合。也称为双重巧合。由于金钱是一种公认的交换媒介，我不需要找到有一双新鞋的人，而且正在寻找Wayne Gretzky曲棍球卡。我只需要找一个正在寻找Gretzky卡的人，他愿意支付足够的钱，这样我就可以在Footlocker买一双新牌。这是一个更容易解决的问题，因此我们的生活变得更加容易，而且我们的经济效率更高，存在资金。至于什么是金钱，什么没有，他的定义由纽约联邦储备银行提供：“美联储公布每周和每月三种货币供应量数据–M1，M2和M3 – 以及作为美国经济非金融部门债务总额的数据……货币供应量指标反映了不同类型货币所具有的不同程度的流动性 – 或可支配性。最窄的指标M1仅限于最流动的货币形式;它包括公众手中的货币;旅行支票;活期存款以及可以写支票的其他存款.M2包括M1，加上储蓄账户，10万美元以下的定期存款以及余额零售货币市场共同基金.M3包括M2加大面额（100,000美元或以上）定期存款，机构货币基金余额，存款机构发行的回购负债以及美国居民持有的欧元美元在美国银行的外国分支机构以及英国和加拿大的所有银行。“因此有几种不同的货币分类。请注意，信用卡不是一种形式的钱。请注意，钱与财富不同。只需印刷更多钱，我们就无法让自己变得更富裕。
Money is a good that acts as a medium of exchange in transactions. Classically it is said that money acts as a unit of account, a store of value, and a medium of exchange. Most authors find that the first two are nonessential properties that follow from the third. In fact, other goods are often better than money at being intertemporal stores of value, since most monies degrade in value over time through inflation or the overthrow of governments. So, money isn’t just pieces of paper. It’s a medium of exchange that facilitates trade. Suppose I have a Wayne Gretzky hockey card that I’d like to exchange for a new pair of shoes. Without the use of money, I have to find a person, or combination of people who have an extra pair of shoes to give up, and just happen to be looking for a Wayne Gretzky hockey card. Quite obviously, this would be quite difficult. This is known as the double coincidence of wants problem: The double coincidence is the situation where the supplier of good A wants good B and the supplier of good B wants good A. The point is that the institution of money gives us a more flexible approach to trade than barter, which has the double coincidence of wants problem. Also known as dual coincidence of wants. Since money is a recognized medium of exchange, I do not have to find someone who has a pair of new shoes and is looking for a Wayne Gretzky hockey card. I just need to find someone who is looking for a Gretzky card who is willing to pay enough money so I can get a new pair at Footlocker. This is a far easier problem, and thus our lives are a lot easier, and our economy more efficient, with the existance of money. As for what constitutes money and what does not ,he following definition is provided by The Federal Reserve Bank of New York: “The Federal Reserve publishes weekly and monthly data on three money supply measures — M1, M2, and M3 — as well as data on the total amount of debt of the nonfinancial sectors of the U.S. economy… The money supply measures reflect the different degrees of liquidity — or spendability – that different types of money have. The narrowest measure, M1, is restricted to the most liquid forms of money; it consists of currency in the hands of the public; travelers checks; demand deposits, and other deposits against which checks can be written. M2 includes M1, plus savings accounts, time deposits of under $100,000, and balances in retail money market mutual funds. M3 includes M2 plus large-denomination ($100,000 or more) time deposits, balances in institutional money funds, repurchase liabilities issued by depository institutions, and Eurodollars held by U.S. residents at foreign branches of U.S. banks and at all banks in the United Kingdom and Canada.” So there are several different classifications of money. Note that credit cards are not a form of money. Note that money is not the same thing as wealth. We cannot make ourselves richer by simply printing more money.