This broad definition includes any physiologically based impairment or any mental or psychological impairment, but it does not include mere physical characteristics or cultural, economic, or environmental impairment. For example, a person with dyslexia may have a disability, but a person who is illiterate does not; a person who is a dwarf may have a disability, but a person who is short does not.

The impairment must cause a substantial limitation to a major life activity. Major life activities include walking, seeing, hearing, or being able to care for oneself. Temporary conditions, such as a broken leg or a cold, would not be considered substantial limitations. Whether an impairment causes a substantial limitation is determined on a case-by-case basis, taking into account how the impairment affects the particular person involved. Thus, for some people, epilepsy will cause a substantial limitation, while for others it will not.

The second meaning of the term includes people who no longer have a disability but have a record of a disability, such as a person who successfully recovered from a disabling disease.

The third meaning of the term includes people who have a condition that does not substantially limit a major life activity but are faced with an employer who believes it does cause such a limitation. For example, this definition would include a worker who has asymptomatic HIV/AIDS and is not hired because the prospective employer mistakenly believes that the worker is unable to care for himself and therefore would cause disruption in the workplace.