Fungibility is the property of a good or a commodity whose individual units are capable of mutual substitution. That is, it is the property of essences or goods which are "capable of being substituted in place of one another." For example, since one ounce of pure gold is equivalent to any other ounce of pure gold, gold is fungible. Other fungible commodities include sweet crude oil, company shares, bonds, precious metals, and currencies. Fungibility refers only to the equivalence of each unit of a commodity with other units of the same commodity. Fungibility does not relate to the exchange of one commodity for another different commodity.