In sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

, 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 rig

Square rig

Square rig is a generic type of sail and rigging arrangement in which the primary driving sails are carried on horizontal spars which are perpendicular, or square, to the keel of the vessel and to the masts. These spars are called yards and their tips, beyond the last stay, are called the yardarms...

ged vessel, i.e., a ship's courses would be the foresail

Foresail

A foresail is one of a few different types of sail set on the foremost mast of a sailing vessel:* A fore and aft sail set on the foremast of a schooner or similar vessel....

, mainsail

Mainsail

A mainsail is a sail located behind the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....

, and, on the rare occasions in which one is shipped, mizen. Gaff-rigged

Gaff rig

Gaff rig is a sailing rig in which the sail is four-cornered, fore-and-aft rigged, controlled at its peak and, usually, its entire head by a spar called the gaff...

 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

Bermuda rig

The term Bermuda rig refers to a configuration of mast and rigging for a type of sailboat and is also known as a Marconi rig; this is the typical configuration for most modern sailboats...

- or lateen-rigged yacht, whether sloop

Sloop

A sloop is a sail boat with a fore-and-aft rig and a single mast farther forward than the mast of a cutter....

, cutter, ketch

Ketch

A ketch is a sailing craft with two masts: a main mast, and a shorter mizzen mast abaft of the main mast, but forward of the rudder post. Both masts are rigged mainly fore-and-aft. From one to three jibs may be carried forward of the main mast when going to windward...

 or yawl

Yawl

A yawl is a two-masted sailing craft similar to a sloop or cutter but with an additional mast located well aft of the main mast, often right on the transom, specifically aft of the rudder post. A yawl (from Dutch Jol) is a two-masted sailing craft similar to a sloop or cutter but with an...

, would not usually be described as having a course.