What is (Not) Money? Medium of Exchange ≠Means of Payment

This note attempts to provide a formulaic definition of money and discuss the distinction between “medium of exchange†and “means of payment.†The former refers to the set of assets in an economy that people regularly exchange for goods and services (a concept of “what†), while the latter is a method that facilitates delivery of money from one to another (a notion of “how†). It suggests that money should be exclusively defined as “medium of exchange,†rather than “means of payment.†With such a distinction established, one can uniformly explain why currency, demand deposits and smart cards are money (because they are a medium of exchange), and why checks, money orders, or debit and credit cards are not money (because they are only a means of payment but not a medium of exchange).