| A | Arterial 
| Others |
| A | Arteriolar
| Others |
| A | Artery
| Others |
| A | As
| Others |
| A | Asbestos
| Others |
| A | Ascaris
| Others |
| A | Asexual
| Others |
| A | Asparagine
| Others |
| A | Assist
| Others |
| A | Atom
| Others |
| A | Atomic
| Others |
| A | Atrial
| Others |
| A | Atrium
| Others |
| A | Atropine
| Others |
| A | augmenting reducing
| Others |
| A | Auricular
| Others |
| A | auris (ear)
| Others |
| A | Australian
| Others |
| A | Autos
| Others |
| A | Ava
| Others |
| A | Avance
| Others |
| A | Avianca Airlines
| Others |
| A | Awesome
| Others |
| A | Axis
| Others |
| a | before (from Latin ante)
| Others |
| A | Blood Type
| Others |
| a | chemical activity
| Others |
| A | for Aircraft
| Others |
| A | form A (normally open) contacts
| Others |
| A | Helmholtz Energy
| Others |
| A | mass number
| Others |
| A | radioactivity
| Others |
| A | The Arts
| Others |
| A & ER | Ammunition and Explosives Regulations
| Others |
| A & G | Administrative and General
| Others |
| A & P | Airframe & Powerplant
| Others |
| A R Mallick | Azizur Rahman Mallick
| Others |
| A Rod | Alex Rodriguez
| Others |
| A$AP | All Strive and Prosper
| Others |
| A%2FC | A/C
| Others |
| A&A | Abbreviations and Acronyms
| Others |
| A&A | Acronyms & Abbreviations
| Others |
| A&A | Advertise and Award
| Others |
| A&A | Amos and Andy
| Others |
| A&A | Arrival and Assembly
| Others |
| A&A | Axis & Allies
| Others |
| A&AR | Accounting and Auditing Releases
| Others |
| A&AS | Advisory and Assistance Service
| Others |
| A&B | Apnea and Bradycardia
| Others |
| A&C | Activation and Checkout
| Others |