| Abbreviation | Definition |
|---|---|
| A | Absorbance |
| A | Ampere |
| A | Atomic |
| Å | angstrom |
| AAA | Advanced Applications of Accelerators |
| AAAC | Astronomy and Astrophysics Advisory Committee |
| AAOD | Aerosol Absorption Optical Depth |
| AAPP | Advances and Applications in Plasma Physics |
| AAPP | Association of Applied Physicists Pakistan |
| AAPT | American Association of Physics Teachers |
| AAS | Atomic Absorption Spectrophotometry |
| ABEC | Annular Bearing Engineering Committee |
| ABF | All But Finitely |
| ABHP | American Board of Health Physics |
| ABMP | American Board of Medical Physics |
| A-BOMB | Atomic Bomb |
| ABS | Absorbance |
| AC | Attenuation Coefficient |
| ACB | Annular Confinement Beam |
| ACCI | Atlantic Canada Coral Initiative |