经济学术语表对货币的定义如下：

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.

金钱的用途

所以，钱不仅仅是纸片。它是促进贸易的交换媒介。假设我有一张韦恩·格雷茨基曲棍球卡，我想换一双新鞋。如果不用钱，我必须找到一个人，或是一群人，他们有一双多余的鞋子要放弃，只是碰巧在找一张韦恩·格雷茨基的曲棍球卡。很明显，这将是相当困难的。这被称为需求的双重巧合问题：

• [T] 双重巧合是指商品A的供应者想要商品B，商品B的供应者想要商品A的情况。重点是货币制度给了我们比易货更灵活的贸易方式，易货具有双重巧合的需求问题。也被称为欲望的双重巧合。

因为金钱是一种公认的交换媒介，我不需要找一个有一双新鞋并且正在寻找韦恩·格雷茨基曲棍球卡的人。我只需要找一个人谁是一个格雷茨基卡谁愿意支付足够的钱，这样我就可以在Footlocker找一个新的双寻找。这是一个容易得多的问题，因此，有了钱，我们的生活更轻松，我们的经济更高效。

如何衡量金钱

至于什么构成货币，什么不构成货币，纽约联邦储备银行给出了以下定义：

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.

因此，有几种不同的货币分类。请注意，信用卡不是一种货币形式。

请注意，金钱与财富不是一回事。我们不能仅仅通过印更多的钱来使自己更富有。