Changed in order to improve or made more fit for a particular purpose; SYN. altered.

ETYM Cf. French adaptation, Late Lat. adaptatio.
In biology, any change in the structure or function of an organism that allows it to survive and reproduce more effectively in its environment. In evolution, adaptation is thought to occur as a result of random variation in the genetic makeup of organisms coupled with natural selection. Species become extinct when they are no longer adapted to their environment—for instance, if the climate suddenly becomes colder.
This produces individuals whose genetically determined characteristics allow them to survive and reproduce more effectively. Thus, the webbed feet of ducks or otters are adaptations to living in water, enabling them to swim more efficiently. In physiology, adaptation is said to occur in sense organs, when the sensitivity of an organ alters in response to changes in environmental conditions. Examples include an increase in the size of the eye's pupil to admit more light as night falls.
1. The process of adapting to something (such as environmental conditions); SYN. adjustment.
2. (Physiology) The responsive adjustment of a sense organ (as the eye) to varying conditions (as of light).
3. A written work (as a novel) that has been recast in a new form; SYN. version.