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.
- "The Mainsail, Foresail, and Mizen, are also called Courses." Lever, Darcy. The Young Sea Officer's Sheet Anchor. 2nd Edition first published 1819. (c) 1998 by Dover Publications, Inc., Mineola, NY 11501: p. 121. N.B. The "mizen" to which Lever refers is a fore-and-aft sail more commonly called "spanker" or "driver" today as, indeed, he did on occasion, q.v., p. 66. The lowest yard on a ship's mizzenmast is the "cross-jack yard" and a squaresail bent thereon is typically referred to as a cross-jack. The true "mizzen yard" evolved into or was replaced by the gaff by the turn of the 19th century, q.v., page 42.