1. Preferential survival of members of a species because of a phenotype that gives them an enhanced capacity to withstand the environment including the ecology. 2. An advantageous change in function or constitution of an organ or tissue to meet new conditions. 3. Adjustment of the sensitivity of the retina to light intensity. 4. A property of certain sensory receptors that modifies the response to repeated or continued stimuli at constant intensity. 5. The fitting, condensing, or contouring of a restorative material, foil, or shell to a tooth or cast so as to be in close contact. 6. The dynamic process wherein the thoughts, feelings, behavior, and biophysiologic mechanisms of the individual continually change to adjust to a constantly changing environment. SYN: adjustment (2). 7. A homeostatic response. [L. ad-apto, pp. -atus, to adjust]
- dark a. the visual adjustment occurring under reduced illumination in which the retinal sensitivity to light is increased. SEE ALSO: dark-adapted eye, Purkinje shift. SYN: scotopic a..
- light a. the visual adjustment occurring under increased illumination in which the retinal sensitivity to light is reduced. SEE ALSO: light-adapted eye, Purkinje shift. SYN: photopic a..
- photopic a. SYN: light a..
- reality a. the ability to adjust to the world as it exists.
- scotopic a. SYN: dark a..
- social a. adjustment to living in accordance with interpersonal, social, and cultural norms.

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ad·ap·ta·tion .ad-.ap-'tā-shən, -əp- n
1) the act or process of adapting: the state of being adapted <his ingenious \adaptation of the electric cautery knife (George Blumer)>
2) 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)
ad·ap·ta·tion·al -shnəl, -shən-əl adj
ad·ap·ta·tion·al·ly adv

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the phenomenon in which a sense organ shows a gradually diminishing response to continuous or repetitive stimulation. The nose, for example, may become adapted to the stimulus of an odour that is continuously present so that in time it ceases to report its presence. Similarly, the adaptation of touch receptors in the skin means that the presence of clothes can be forgotten a few minutes after they have been put on.

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ad·ap·ta·tion (ad″ap-taґshən) [L. adaptare to fit] 1. the adjustment of an organism to its environment, or the process by which it enhances such fitness. 2. the normal adjustment of the eye to variations in intensity of light. 3. the decline in the frequency of firing of a neuron, particularly of a receptor, under conditions of constant stimulation. 4. in dentistry, (a) the proper fitting of a denture, (b) the degree of proximity and interlocking of restorative material to a tooth preparation, (c) the exact adjustment of bands to teeth. 5. in microbiology, the adjustment of bacterial physiology to a new environment; see genetic a. and phenotypic a.

Medical dictionary. 2011.