n. The act of circulating or moving in a circle or circuit; movement in such a manner as to go forth and return to the starting-point: as, the circulation of the blood (see phrases below).n. The act or state of being diffused or distributed; the act of passing from point to point or from person to person; diffusion: as, the circulation of sap in a tree; the circulation of money; the circulation of a piece of news.n. The extent to which a thing circulates or is diffused or distributed: as, the circulation of the two periodicals was about 300,000 copies.n. A repetition of a series of things or events in the same order.n. The amount of coin, notes, bills, etc., in actual use as currency: as, the circulation of the national banks.n. In chem., the repeated vaporization and condensation of a substance in distillation.n. In mathematics, the amount of flow round a closed path or circuit; the line-integral round a closed curve of the component velocity of a fluid along the curve.