Disability discrimination law protects a qualified individual with a disability, defined as a physical or mental impairment substantially limiting a major life activity, a record of such an impairment, or being regarded as having one.
The definition is construed broadly. Statutory amendments directed courts to stop treating coverage as a demanding threshold. Mitigating measures other than ordinary eyeglasses are disregarded, so an employee whose condition is well controlled by medication is still assessed by the underlying impairment.
Major life activities include working, but also caring for oneself, performing manual tasks, seeing, hearing, sleeping, concentrating, and the operation of major bodily functions.
Episodic conditions and those in remission qualify if they would substantially limit when active.
Regarded as covers an employee subjected to an adverse action because of a perceived impairment, whether or not it limits anything — though accommodation is not owed on that basis alone.
Qualified means able to perform the essential functions with or without reasonable accommodation. This, not the definition of disability, is where the real analysis belongs.
Practical consequence. Employers that litigate coverage usually lose time and credibility. The defensible ground is the interactive process, the essential functions, and the documented business reason.