A sloop is a sailboat with a single mast typically having only one headsail in front of the mast and one mainsail aft of (behind) the mast.[note 1] Such an arrangement is called a fore-and-aft rig, and can be rigged as a Bermuda rig with triangular sails fore and aft, or as a gaff-rig with triangular foresail(s) and a gaff rigged mainsail.
In naval terminology, "sloop-of-war" refers to the purpose of the craft, rather than to the specific size or sail-plan, and thus a sloop should not be confused with a sloop-of-war. The term is also used loosely with other sail plans, as with the Friendship Sloop, : 48-53 which is a cutter.
The name originates from the Dutch sloep, which is related to the Old English slūpan, to glide. A sloop is usually regarded as a single-masted rig with a single headsail and a fore-and-aft mainsail. In this form, the sloop is the commonest of all sailing rigs – with the Bermuda sloop being the default rig for leisure craft, being used on types that range from simple cruising dinghies to large racing yachts with high-tech sail fabrics and large powerful winches.: 48–53 If the vessel has two or more headsails, the term cutter may be used, especially if the mast is stepped further aft.
Before the introduction of the marconi rig, a sloop might carry one or more square-rigged topsails which will be hung from a topsail yard and be supported from below by a crossjack.
A sloop's headsail may be masthead-rigged or fractional-rigged. On a masthead-rigged sloop, the forestay (on which the headsail is carried) attaches at the top of the mast. On a fractional-rigged sloop, the forestay attaches to the mast at a point below the top. A sloop may use a bowsprit, a spar that projects forward from the bow.