M2 is described as a definition of money that is, compared with M1:

1. The two measures differ in how much they include. 2. M1 covers coins, currency, checkable deposits and traveler's checks. 3. A broader definition of money is M2. 4. M2 includes everything in M1 but also adds other types of deposits. _Source: OpenStax Principles of Macroeconomics for AP Courses 2e (CC BY 4.0), Ch 13 'Money and Banking'_