ADA (plural ADAs)
- Initialism of adenosine deaminase, the enzyme that specifically affects RNA. See ADAR.
- Initialism of assistant district attorney.
- Acronym of anti-doping agency.
- (assistant district attorney): EADA / E.A.D.A. / E. A. D. A. (executive assistant district attorney)
- (anti-doping agency): WADA, USADA, RUSADA
- Initialism of American Dental Association.
- Initialism of Americans for Democratic Action.
- Initialism of Americans with Disabilities Act.
- Initialism of American Diabetes Association.
- Initialism of Air Defense Artillery.
- Initialism of Association of Drainage Authorities.