Final answer:
Acanthosis is the thickening of the epidermis, while callus is hardened skin that forms from repeated pressure or friction.
Step-by-step explanation:
Acanthosis is a condition characterized by the thickening of the epidermis, the outermost layer of the skin. This occurs due to an increase in the number of skin cells, which can be caused by various factors such as hormonal changes or friction.
Callus, on the other hand, is an area of hardened skin that develops in response to repeated pressure or friction. It is a protective response of the skin to prevent damage. Calluses commonly form on the hands or feet.