A sloop (from Dutch sloep, in turn from French chaloupe) is a sailing boat with a single mast and a fore-and-aft rig. A sloop has only one head-sail: if a vessel has two or more head-sails, the term 'cutter' is used, and its mast may be set further aft than on a sloop.
The most common rig of modern sailboats is the Bermuda-rigged sloop. Typically, a modern sloop carries a mainsail on a boom aft of the mast, with a single loose-footed head-sail (a jib or a genoa jib) forward of the mast.
Sloops are either 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. The mainsail may be smaller than the headsail, which is then called a genoa jib. On a fractional-rigged sloop, the forestay attaches to the mast at a point below the top, typically 3/4 of the way to top, or perhaps 7/8 or some other fraction. The mast of a fractional-rigged sloop may be placed farther forward; compared to a masthead-rigged sloop, this results in a rather smaller jib relative to the size of the mainsail.
After the cat rig, which has only a mainsail, the sloop rig is one of the simpler sailing rig configurations. A sloop typically has two sails, a mainsail and a headsail (known as either a jib or a genoa, depending on size), while the cutter has a mainsail and two or more headsails. Next in complexity are the ketch, the yawl and the schooner, each of which has two masts and a minimum of three sails. A sloop has a simple system of mast rigging — a forestay (connecting the mast to bow), a backstay (mast to stern) and shrouds (mast to sides).