1. adjustment of a sense organ to the intensity or quality of stimulation, resulting in a temporary change in sensory or perceptual experience, as in visual adaptation when the pupil of the eye adjusts to dim or bright light.

2. reduced responsiveness in a sensory receptor or sensory system caused by prolonged or repeated stimulation. The adaptation may be specific, for example, to the orientation of a particular stimulus. Also called sensory adaptation.

3. modification to suit different or changing circumstances. In this sense, the term often refers to behavior that enables an individual to adjust to the environment effectively and function optimally in various domains, such as coping with daily stressors. It is also applied more widely, for example, in ergonomics, to denote a system that alters information presentation, interface design, or output according to the capabilities or characteristics of the user, system, or environmental state. Compare maladaptation.

4. adjustments to the demands, restrictions, and mores of society, including the ability to live and work harmoniously with others and to engage in satisfying social interactions and relationships. Also called social adaptation.

5. the modification of an organism in structure or function that increases its ability to reproduce successfully and its offspring’s ability to survive and reproduce successfully.

6. in Piagetian theory, the process of adjusting one’s cognitive structures to meet environmental demands, which involves the complementary processes of assimilation and accommodation. —adapt vb. —adaptational adj. —adaptive adj.