: the act or process of adapting : the state of being adapted <his ingenious adaptation of the electric cautery knife to…surgery—George Blumer>
: adjustment to environmental conditions: as a: adjustment of a sense organ to the intensity or quality of stimulation b: modification of an organism or its parts that makes it more fit for existence under the conditions of its environment—compare adjustment 1b
In biology, the process by which an animal or plant becomes fitted to its environment. It is the result of natural selection acting on inherited variation. Even simple organisms must be adapted in many ways, including structure, physiology, and genetics; movement or dispersal; means of defense and attack; and reproduction and development. To be useful, adaptations must often occur simultaneously in different parts of the body.