Circulation

Circulation (Latin: circulare, revolve ') is

In mathematics and physics, a measure of the rotation, see circulation ( field theory )
In hydrology, the circulation of the water, see circulation ( hydrology )
In meteorology is meant by circulating a circular air flow, see circulation ( meteorology )
In architecture and building physics, the air circulation in the building, see air exchange
In the economics of the circulation of currency, see circulation rate (money), or of goods ( circulation process).
In the drinking water system for a water heater returning hot water pipe and to maintain tempered water to the consumer.