Chair

A chair is a specific type of seat designed for one person.

It typically consists of a flat or slightly angled seat and a back-rest. Most chairs stand on one or more legs to support the occupant. They can be made from wood, metal, or synthetic materials. Many chairs feature padding or upholstery made of various fabrics.

This variety allows chairs to serve many different human needs.

Designers use a field called ergonomics to ensure chairs are comfortable. Ergonomics is the study of how the human body interacts with objects. Designers must consider how a chair distributes an occupant's weight. They use anthropometric measurements, which are data about the human body. One key measurement is the popliteal height. This is the distance from the underside of the foot to the underside of the thigh.

If a seat is too high, feet may dangle and increase pressure on the knees. If a seat is too low, it may press too hard on the ischial tuberosities, or seat bones.

There are many specialized types of chairs used today. An armchair includes armrests fixed to the seat. A recliner uses a mechanism to lower the back and raise a footrest. Rocking chairs have legs fixed to two long, curved slats.

Wheelchairs use wheels fixed to an axis under the seat to assist movement. Some modern chairs use motors to provide massage functions. Other designs, like the bean bag or the egg-shaped pod chair, emerged from the modern movement of the 1960s.

Chairs have a long history as symbols of power and dignity. In ancient Egypt, they were used by the elite during the Early Dynastic Period.

These chairs were often made of ebony, ivory, or gilded wood. They could be decorated with magnificent patterns or animal legs. Pharaohs often sat on thrones with footstools during state occasions. Most average Egyptian families did not own chairs and sat on stools instead. In China, chairs were rare until the 12th century. Scholars debate if they arrived via Central Asian camp stools, Christian missionaries, or Buddhist furniture from India.

In Europe, the Renaissance changed how chairs were used. They shifted from being symbols of state privilege to standard furniture. The Industrial Revolution made chairs much more available to the public. By the 1830s, companies like Sears, Roebuck, and Co. sold factory-manufactured "fancy chairs."

In the 1800s, American households often provided a chair for every family member at dinner. The 20th century brought even more technology, such as molded plastic and all-metal folding chairs.

Designers also focus on seat depth and width for comfort. They use the buttock popliteal length to determine how deep a seat should be. This is the horizontal distance from the back of the buttocks to the back of the lower leg. Mass-produced chairs are typically 15 to 17 inches deep. They also consider hip breadth to decide how wide a chair or its armrests should be. Even in airplanes, designers must manage "seat pitch," which is the distance between rows.

Sometimes, chairs are used as a medium for extreme art and experimentation. Designer Raimonds Cirulis created a hanging chair made of volcanic rock. Another designer, Peter Brenner, made a chair out of 60 pounds of confectioners' sugar.

While these are rare, they show the creative potential of the form. Beyond furniture, the word "chair" still carries its historical meaning of authority. We see this in terms like "chairman" for leaders of boards or committees. Even academic professors may hold a "chair," which is an endowed position.