ADA is a three-letter abbreviation with multiple meanings, as described below:

• ADA, a character in the Zone of the Enders game franchise.
• Aerolineas de Antioquia - A Colombian Airline
• Aeronautical Development Agency of India's Ministry of Defence
• Adangme language as its ISO 639 code
• Adenosine deaminase
• Advanced Distribution Automation
• Air Defense Artillery a branch of the United States Army
• American Decency Association
• American Dental Association
• American Diabetes Association
• American Dietetic Association
• Americans For Democratic Action
• Americans with Disabilities Act
• Amigos dos Amigos, one of the three main drug cartels in the favelas of Rio de Janeiro
• Aotearoa Digital Arts - http://ada.waikato.ac.nz/
• Aqua Design Amano, a company
• Arrangements for deposit accounts, a special regulation under the European Patent Convention
• Assistant district attorney
• Average Daily Attendance
• International Adana Airport, as the IATA airport code for the airport in Adana, Turkey

ADA