Definition of "Circulation" :

noun: the spread or transmission of something (as news or money) to a wider group or area

noun: the dissemination of copies of periodicals (as newspapers or magazines)

noun: free movement or passage (as of cytoplasm within a cell or sap through a plant)

"Ocean circulation is an important part of global climate."

noun: movement through a circuit; especially the movement of blood through the heart and blood vessels

noun: number of copies of a newspaper or magazine that are sold

"By increasing its circulation the newspaper hoped to increase its advertising."

noun: (library science) the count of books that are loaned by a library over a specified period