A couch or sofa is a piece of furniture for seating two or more people in the form of a bench, with or without armrests, that is partially or entirely upholstered, and often fitted with springs and tailored cushions. Although a couch is used primarily for seating, it may be used for reclining and napping.

In homes, couches are normally found in the family room, living room, den, sitting room or the lounge. They are also found in hotels, lobbies of commercial offices, waiting rooms, and some bars.

The term couch is used in North America and Australia, whilst the term sofa is generally used in the United Kingdom. The word originated in Middle English from the Old French noun couche, which derived from the verb meaning "to lie down". It originally denoted an item of furniture for lying or sleeping on, somewhat like a chaise longue, but now refers to sofas in general.

Other terms which can be synonymous with the above definition are settee, chesterfield, divan, davenport, lounge, and canapé. The word sofa is from Turkish derived from the Arabic word suffa for "wool", originating in the Aramaic word sippa for "mat". The word settee comes from the Old English word, "setl", which was used to describe long benches with high backs and arms, but is now generally used to describe upholstered seating.

The settee sail was a lateen sail with the front corner cut off, giving it a quadrilateral shape. It can be traced back to Greco-Roman navigation in the Mediterranean in late antiquity; the oldest evidence is from a late-5th-century AD ship mosaic at Kelenderis, Cilicia. It lasted well into the 20th century as a common sail on Arab dhows. The settee sail requires a shorter yard than does the lateen, and both settee and lateen have shorter masts than square-rigged sails.

Settees (or saëtia) then were a sharp-prowed, single-decked merchant sailing vessel found in the Mediterranean (more in the Levant than in the Western Mediterranean), in the 18th and 19th centuries. The Spaniards also used them in the New World.

Settees had two lateen-rigged masts, like xebecs or galleys, but carrying settee sails. They sailed well to windward and could sail downwind. Some polaccas carried a settee sail, giving rise to the polacca-settee (or polacre-settee).

Between the 1880s and the 1960s, Gozo boats had a settee rig.