1. The continuous movement of blood through the heart and blood vessels, which is maintained chiefly by the action of the heart, and by which nutrients, oxygen, and internal secretions are carried to and wastes are carried from the body tissues.
2. An act or instance of circulating, moving or flowing in a circle or circuit.
3. Any similar circuit, passage, or flow, as of sap in plants or air currents in a room.
4. The transmission or passage of anything from place to place or person to person; such as, the circulation of a rumor; the circulation of money.
5. The distribution of copies of a periodical among subscribers.
6. The number of copies of each issue of a newspaper, magazine, etc., distributed to those who buy such media.
7. The movement of coins, notes, bills, etc., in use as money; also known as, "currency".
8. The lending of library books and other materials or the number of books and materials that a library has loaned out to patrons.

Any atmospheric flow used to refer to the general circulation of the Earth and regional movements of air around areas of high and low pressure: On average, the atmospheric general circulation corresponds to large-scale wind systems arranged in several east–west belts that encircle the Earth.

A pattern of global ocean circulative currents or courses driven by density differences in water: The Gulf Stream is one example of thermohaline circulation that is created by variations or changes in temperature and salinity in the ocean.