The foot is a biological structure found in many animals that is used for locomotion. The plural of foot is feet, and this pair is one of seven mutated English plurals.
The structural quality of a foot varies from animal to animal. Many vertebrates that have legs also have a foot located at the end of each leg. For these animals, the foot is a complex structure of bone, muscle, and other connective tissue. Among animals that have soft or padded feet, the foot is commonly called a paw. In mollusks, on the other hand, the foot is a purely muscular structure.
Human beings use their legs and feet for bipedal locomotion, also known as walking. The structures of the human foot and hand are variations on the same basic five-digit anatomy, in common with many other vertebrates. They are also the most complex, comprising half the bones in the body. The medical specialty related to treatment of the feet is podiatry.
In many societies, it is customary to cover the foot in most social situations; particularly outside, in many cultures (including North American, European, Japanese and others) people wear protective clothing over the foot. Such footwear has special names, such as sandals, shoes, and boots. Consistent wearing of footwear, particularly in hot climates or during exercise, can lead to foot odor. If footwear is ill-fitting or badly designed, it can cause both short-term (blisters, for example) and long-term foot problems. On the other hand, carefully designed orthopedic footwear is an effective treatment for many foot, leg, and back problems.
Customs about foot covering while indoors vary significantly from place to place. For example, in much of Canada, it is customary to remove one's shoes or boots when entering a home, while in the neighboring United States this is rare in most parts of the country. In Japan, the custom is so widespread that floors are often made of materials that are too soft to survive being walked on by shod feet. In cultures where shoes are rarely removed, bare feet may be considered unsightly or offensive.
Striking an object or a person with the foot is called kicking. Certain martial arts, such as Savate, emphasize kicking, reasoning that the foot is the only part of the body normally covered by protective clothing. On the other hand, some martial arts (including Karate, Judo) are customarily trained in bare feet, as well as beach sport (for example beach volleyball). Many sports, including football (in all its forms, including soccer), and rugby, involve kicking a ball or other object with the foot.
The foot provides a convenient way to measure short distances on the ground, by placing one foot directly in front of the other; this led to the adoption of the foot as a unit of length.