The world economy or global economy is the economy of the world, considered as the international exchange of goods and services that is expressed in monetary units of account (money). In some contexts, the two terms are distinguished: the "international" or "global economy" being measured separately and distinguished from national economies while the "world economy" is simply an aggregate of the separate countries' measurements. Beyond the minimum standard concerning value in production, use, and exchange the definitions, representations, models, and valuations of the world economy vary widely. It is inseparable from the geography and ecology of Earth.