biological process of molting (moulting)—i.e., the shedding or casting off of an outer layer or covering and the formation of its replacement. Molting, which is regulated by hormones, occurs throughout the animal kingdom. It includes the shedding and replacement of horns, hair, skin, and feathers.

The process of shedding an external skeleton for the purpose of growth or change in shape (see metamorphosis) is called ecdysis; it occurs in such invertebrates as arthropods, nematodes, and tardigrades.