In economics, fungibility is the property of a good or a commodity whose individual units are essentially interchangeable, and each of whose parts are indistinguishable from any other part. Fungible tokens can be exchanged or replaced; for example, a $100 note can easily be exchanged for twenty $5 bills. In contrast, non-fungible tokens cannot be exchanged in the same manner.

For example, gold is fungible because its value doesn’t depend on any specific form, whether of coins, ingots, or other states. However, a unique item such as a gold statue by a famous artist would not be considered fungible. In short, a thing is fungible when all equivalent amounts of that thing are interchangeable. Fungible commodities include sweet crude oil, company shares, bonds, other precious metals, and currencies.

Fungibility refers only to the equivalence and indistinguishability of each unit of a commodity with other units of the same commodity, and not to the exchange of one commodity for another.