A circular course is a route that follows a continuous loop, often in the form of a CIRCLE. The term 'GYRE' is used to describe this type of course, as it is derived from the Greek word for 'CIRCLE'. A GYRE is a circular or spiral pattern that can be seen in nature, such as in ocean currents or the flight paths of birds. In navigation, a GYRE is a circular course that is used to travel around an area or to return to a starting point.