Who the ADA protects, and the three claims it creates
Title I of the Americans with Disabilities Act, 42 U.S.C. 12112, bars an employer with 15 or more employees (42 U.S.C. 12111(5)) from discriminating against a qualified individual on the basis of disability in hiring, advancement, discharge, pay, training, and every other term of employment. Many state laws start lower. Two definitions decide whether the statute reaches you; three kinds of conduct violate it.
Disability: impairment, record, or regarded as
Under 42 U.S.C. 12102 a disability is a physical or mental impairment that substantially limits one or more major life activities, a record of such an impairment, or being regarded as having one. Since the 2008 amendments the definition is read broadly: an episodic condition counts if it would limit you when active, and mitigating measures such as medication are disregarded. The regarded-as prong covers a perceived impairment unless it is both transitory (six months or less) and minor.
Qualified: able to do the essential functions, with or without accommodation
A qualified individual under 42 U.S.C. 12111(8) can perform the essential functions of the job with or without reasonable accommodation. The employer’s judgment about which functions are essential, and a job description written before the posting, are given weight. If no accommodation lets you do the core of the job, the claim fails here.
Claim one: failure to accommodate
Section 12112(b)(5)(A) makes it discrimination to not make reasonable accommodations to the known limitations of an otherwise qualified employee or applicant, unless the employer can demonstrate undue hardship. Denying a job because you need an accommodation is a separate violation. The next section walks through it.
Claim two: disparate treatment
Firing, demoting, refusing to hire, or paying less because of an actual or perceived disability. Section 12112(b) also names segregating disabled workers, using standards that screen them out unless job-related and consistent with business necessity, and discriminating against someone because of a relative’s disability.
Claim three: unlawful medical inquiries and exams
Section 12112(d) limits what an employer may ask. Before an offer it may not ask whether you have a disability or require a medical exam, though it may ask whether you can perform job functions. After an offer it may require an exam only if every entering employee gets one and the results stay confidential. Once you are employed, exams and disability questions must be job-related and consistent with business necessity.