A chair is a piece of furniture with a raised surface supported by legs, commonly used to seat a single person. Chairs are supported most often by four legs and have a back; however, a chair can have three legs or can have a different shape. Chairs are made of a wide variety of materials, ranging from wood to metal to synthetic material (e.g. plastic), and they may be padded or upholstered in various colors and fabrics, either just on the seat (as with some dining room chairs) or on the entire chair. Chairs are used in a number of rooms in homes (e.g. in living rooms, dining rooms, and dens), in schools and offices (with desks), and in various other workplaces.
A chair without a back or arm rests is a stool, or when raised up, a bar stool. A chair with arms is an armchair; one with upholstery, reclining action, and a fold-out footrest is a recliner. A permanently fixed chair in a train or theater is a seat or, in an airplane, airline seat; when riding, it is a saddle or bicycle saddle; and for an automobile, a car seat or infant car seat. With wheels it is a wheelchair; or when hung from above, a swing. An upholstered, padded chair for two.
Chair seats vary widely in construction and may or may not match construction of the chair's back (backrest).Some systems include:Center seats where a solid material forms the chair seat Solid wood, may or may not be shaped to human contoursWood slats, often seen on outdoor chairs Padded leather, generally a flat wood base covered in padding and contained in soft leather
A chair may or may not have armrests; chairs with armrests are termed "armchairs". In French, a distinction is made between fauteuil and chaise, the terms for chairs with and without armrests, respectively. In Germany, an armchair was once called a Krankensessel, or sick-chair, because it was intended for people who were too ill to stand or sit without extra support.
If present, armrests will support part of the body weight through the arms if the arms are resting on the armrests. Hence in some chair designs, the armrest is not continuous to the chair back, but is missing in the elbow area.