Pronunciation: (sûr"kyu-lā'shun),[key] —n. 1. an act or instance of circulating, moving in a circle or circuit, or flowing.
2. 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.
3. any similar circuit, passage, or flow, as of the sap in plants or air currents in a room.
4. the transmission or passage of anything from place to place or person to person: the circulation of a rumor; the circulation of money. 5. the distribution of copies of a periodical among readers.
6. the number of copies of each issue of a newspaper, magazine, etc., distributed.
7. coins, notes, bills, etc., in use as money; currency.
8. Library Science. a. the lending of library books and other materials.
b. the number of books and materials that a library has lent.
c. the processes connected with providing for the use of library materials, including reserve operations, recall, and record-keeping.
9. Hydraul.a quantity analogous to work and equal to the line integral of the component of fluid velocity about a closed contour.
10. in circulation, participating actively in social or business life: After a month in the hospital, he's back in circulation.