the act of adapting.

the state of being adapted; adjustment.

something produced by adapting

an adaptation of a play for television.

Biology .

any alteration in the structure or function of an organism or any of its parts that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.

a form or structure modified to fit a changed environment.

the ability of a species to survive in a particular ecological niche, esp. because of alterations of form or behavior brought about through natural selection.

Physiology . the decrease in response of sensory receptor organs, as those of vision, touch, temperature, olfaction, audition, and pain, to changed, constantly applied, environmental conditions.

Ophthalmology . the regulating by the pupil of the quantity of light entering the eye.

Also, adaption

noun

accommodation , adjustment , conformation