A couch, also known as a sofa, settee, futon, or chesterfield (see Etymology below), is a piece of furniture for seating two or three people. It is commonly found in the form of a bench, with upholstered armrests, and often fitted with springs and tailored cushions. Although a couch is used primarily for seating, it may be used for sleeping. In homes, couches are normally put in the family room, living room, den or lounge. They are sometimes also found in non-residential settings such as hotels, lobbies of commercial offices, waiting rooms, and bars.
The term couch originally denoted an item of furniture for lying or sleeping on.  Couch is predominantly used in North America, South Africa, Australia and Ireland, whereas the terms sofa and settee (U and non-U) are most commonly used in the United Kingdom and India. The word couch originated in Middle English from the Old French noun couche, which derived from the verb meaning "to lie down". The word sofa comes from Turkish and is derived from the Arabic word suffah ("ledge/bench"), cognates with the Aramaic word sippa ("mat"). Joseph Pubillones in A Little Shimmer Goes a Long Way specifies that the main difference between the couch and the sofa is that "couches can be used for reclining or laying upon" so a couch would "best be used to describe an upholstered piece in a family room", while the term sofa "used predominantly in England and Ireland denotes a tone of formality, hence a sofa is more appropriate word for the upholstered piece in the living room".
The most common types of couches are the two-seater, sometimes referred to as a loveseat, and the sofa. The loveseat is designed for seating two people, while the sofa has more than two cushion seats. A sectional sofa, often just referred to as a "sectional", is formed from multiple sections (typically two, three, and four) and usually includes at least two pieces which join at an angle of 90 degrees or slightly greater. Sectional sofas are used to wrap around walls or other furniture.
Other variants include the divan, the fainting couch (backless or partial-backed) and the canapé (an ornamental three-seater). To conserve space, some sofas double as beds in the form of sofa beds, daybeds, or futons.
A furniture set consisting of a sofa with two matching chairs is known as a "chesterfield suite" or "living-room suite". In the UK, the word chesterfield was used to refer to any couch in the 1900s. A chesterfield now describes a deep buttoned sofa, usually made from leather, with arms and back of the same height. The first chesterfield, with its distinctive deep buttoned, quilted leather upholstery and lower seat base, was commissioned by Philip Stanhope, 4th Earl of Chesterfield (1694–1773).
In Canadian English, chesterfield as equivalent to a couch or sofa is widespread among older Canadians. According to a 1992 survey conducted in the Golden Horseshoe region of Ontario, the term is quickly vanishing. 
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A couch consists of the frame, padding and covering. The frame is usually made of wood, but can also be made of steel, plastic or laminated boards. Sofa padding is made from foam, down, feathers, fabric or a combination thereof. Sofa coverings are usually made out of soft leather, corduroy or linen.
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- AMHER, couch: Middle English from Old French culche, couche > couchier, coucher.
- AMHER, sofa: Turkish, from Arabic suffah, from Aramaic sippa, sippəta.
- Pubillones, Joseph (2016). "Sofa, Couch or Divan?". A Little Shimmer Goes a Long Way. p. 30. ISBN 978-1-9456-30330. Retrieved June 20, 2018 – via Google Books.
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- The dictionary definition of couch at Wiktionary