What is Circulation?
{{enWiktionary|circulation}} '''Circulation''' may be used in reference to: *[[Circulatory system]], a biological organ system whose primary function is to move substances to and from cells *[[Circulation (fluid dynamics)]], the path integral of the fluid velocity around a closed curve *[[Exhaust gas recirculation]], a [[nitrogen oxide]] reduction technique *[[Atmospheric circulation]], the large-scale movement of air *[[Newspaper circulation]], the average number of copies of a newspaper distributed on a day *[[Magazine circulation]], the average number of copies of a periodical distributed per edition/ volume *[[Library circulation]], the activities around the lending of library books and other material to users of a lending library *[[Circulation (currency)]], the transfer of currency through the hands of civilians {{disambig}}