Money

The oil that greases the economy’s wheels, and acts as the unit of account for economic activity. Money can be any token that is accepted as payment; past examples have included seashells and the giant stones on the island of Yap. For a while, money was linked to precious metals but modern money is largely fiat currency and is electronic in form. Whatever its form, money needs to be a reasonably stable store of value and an acceptable medium of exchange.