| Abbreviation | Definition |
|---|---|
| AR | approvable letter |
| ARAB(OC) | Accounting Reports and Analysis Branch (OC) |
| ARC | American Red Cross |
| ARCH | Administrative Resources Core Hub |
| ARCRT | American Registry of Clinical Radiography Technologists |
| ARDB | Anesthesiology and Respiratory Devices Branch |
| ARDB(CDRH) | Anesthesiology and Respiratory Devices Branch (CDRH) |
| ARDS | Acute Respiratory Distress Syndrome |
| ARENA | Applied Research Ethics National Association |
| ARF | Acute Renal Failure |
| ARIES | Administrative Resources Information Exchange System |
| ARL | Arkansas Regional Laboratory |
| ARL(ORA) | Arkansas Regional Laboratory (ORA) |
| ARRT | American Registry of Radiologic Technologists |
| ART | Assisted Reproductive Therapy |
| ARTCA | Antimicrobial Regulations Technical Correction Act of 1998 |
| AS | Administrative Staff |
| AS | Aortic Stenosis |
| AS(CVM) | Administrative Staff (Center for Veterinary Medicine) |
| AS(CVM) | Administrative Staff (CVM) |