The second function of money named is that money must serve as a:

1. The three functions are given in a fixed order. 2. First, money serves as a medium of exchange. 3. Second, money must serve as a store of value. 4. Third, money serves as a unit of account. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 13 'Money and Banking'_