The ADA defines "disability" in three ways. First, a person who has a physical or mental impairment; more on that later. Second, a person who has a history or record of such an impairment. Third, a person who is perceived by others as having an impairment. The biggest factor in defining disability is whether the impairment limits one or more major life activities. For example, if you are deaf, you cannot hear. If you are blind, you cannot see. If you have a physical disability, you might struggle to walk. If you have a mental disability, you might have difficulty learning. The point being, if your impairment prevents you from working, accessing education or opportunities in the public space, then you may have a disability as outlined in the ADA. There is no exhaustive list of what counts and does not count as a disability. The definition was purposely vague. It has less to do with actual diagnoses of disability. It has the flexibility to be able to consider individual circumstances.