Corns (clavi) are keratinous thickenings of the skin of the toes that are caused by repeated friction or pressure to the area. The base of the corn is seen on the surface of the skin while the apex points inward, causing discomfort. Corns are classified as either hard or soft, depending upon their location and appearance. Hard corns typically affect the tops of the toes and are composed of a dense core that presses on sensory nerves, causing extreme pain. Soft corns occur between the toes and are continuously softened by sweat. They are macerated and white in appearance.

Factors that can lead to and exacerbate corns include ill-fitting shoes, not wearing shoes, the bunching up of socks, bony prominences in the feet or other faulty foot mechanics, and repetitive physical activities that stress the skin.