Exaptation is a diachronic process whereby morphological material that has become functionless is used for some new function that is quite different from its original function.
The term was first used in linguistics by Lass (1990) (originally 1988). It was adopted from Gould & Vrba's (1982) biological term exaptation, a variation on adaptation.
- Gould, Stephen J. & Vrba, Elisabeth. 1982. "Exaptation: a missing term in the science of form." Paleobiology 8: 4-15.
- Lass, Roger. 1988. "How to do things with junk: Exaptation in language evolution." Stellenbosch Papers in Linguistics 17: 33-63.
- Lass, Roger. 1990. "How to do things with junk: Exaptation in language evolution." Journal of Linguistics 26: 79-102.