callous

Callous is an adjective used to describe someone who is emotionally insensitive or indifferent to others' feelings. It can also refer to a physical condition in which the skin becomes thickened and hardened from repeated friction or pressure. In that sense, the skin form is commonly written as callus in American English, or callosity as a more formal noun.

As a character trait, callous describes actions or attitudes that show a lack of empathy, consideration, or mercy. Phrases such as a callous remark or callous disregard are widely used in everyday speech and in clinical or psychological writing. The related noun callousness denotes the state or quality of being callous.

In medical usage, the skin condition is usually harmless but can cause discomfort if the area becomes very thick or cracked. Treatments include cushioning, moisturizers, and gentle resurfacing or removal of excess skin. People with diabetes, neuropathy, or poor circulation should monitor feet or hands with calluses closely, since unnoticed injuries in thickened areas can lead to infections or ulcers. Overall, the term covers both a behavioral descriptor and a physiological phenomenon, with attention given to context to avoid ambiguity.