| ADA | Adenosine Deaminase | In English | → Genetics → Enzymes |
| ADA | Adaptive Diagnostic Authoring | In English | |
| ADA | Azimuth Drive Assembly | In English | |
| ADA | Austrian Development Agency | In English | → International relations → Development |
| ADA | American Diabetes Association | In English | → Associations → Pathology |
| ADA | American Dietetic Association | In English | → Associations → Nutrition |
| ADA | American Dental Association | In English | → Associations → Dentistry |
| ADA | Armenian Development Agency | In English | → 33972 → International economic cooperation |