Disability is an impairment that may be cognitive, developmental, intellectual, mental, physical, sensory, or some combination of these.
It substantially affects a person's life activities and may be present from birth or occur during a person's lifetime.
The discussion over disability's definition arose out of disability activism in the United States and the United Kingdom in the 1970s, which challenged how the medical concept of disability dominated perception and discourse about disabilities.
Debates about proper terminology and their implied politics continue in disability communities and the academic field of disability studies.
Quetelet postulated that one could take the sum of all people's attributes in a given population (such as their height or weight) and find their average, and that this figure should serve as a norm toward which all should aspire.