What is the medical term for hardened skin at a specific area?

The term "callus" refers specifically to an area of hardened skin that develops as a response to repeated friction, pressure, or irritation. This thickening occurs in order to protect the underlying skin from injury or damage. Calluses commonly form on the hands, feet, or other areas frequently subjected to stress. Their primary characteristic is the increased thickness, making them tougher than the surrounding skin.

In contrast, a cataract pertains to the clouding of the lens in the eye, which affects vision. Exostosis refers to a bony growth that develops on the surface of a bone, not a condition related to skin. Dermatitis is an inflammation of the skin, which can cause redness, swelling, or itchiness, rather than a localized area of hardened skin. Thus, the focus of the definition and characteristics helps to clearly identify why "callus" is the correct term for hardened skin in a specific area.