Course (sail)

In sailing, a course is the lowermost sail on a mast. 
This term is used predominantly in the plural to describe the lowest sails on a square rigged vessel, i.e., a ship's "courses" would be the foresail, mainsail, and, on the rare occasions in which one is shipped, mizzen. Gaff-rigged vessels may use the term (for the lowest sail rigged aft of each mast), but are more likely to refer simply to a mainsail, foresail, etc. A Bermuda- or lateen-rigged yacht, whether sloop, cutter, ketch or yawl, would not usually be described as having a course.