| Abbreviation | Definition |
|---|---|
| ARPES | Angle Resolved Photo Electron Spectroscopy |
| ARROW | Anti-Resonant Reflecting Optical Waveguide |
| ART | Adaptive Resonance Theory |
| ARUPS | Angle-Resolved Ultra-violet Photoemission Spectroscopy |
| ARXPS | Angle Resolved X-ray Photoemission Spectroscopy |
| ASA | Accessible Surface Area |
| ASA | Aperture Setting Adjustment |
| ASA | Apparent Strength of Adhesion |
| ASCA | Advanced Spacecraft for Cosmology and Astrophysics |
| ASD | Active Surface Definition |
| ASD | Astrophysics Science Division |
| ASL | Ambient Stress Level |
| ASP | Advanced Spectroscopic Portal |
| ASPC | Accelerated Studies in Physics and Chemistry |
| ASTP | Advanced Studies In Theoretical Physics |
| ASWT | Arbitrary Shape Wavelet Transform |
| AT.WT. | Atomic Weight |
| ATAP | Accelerator Technology and Applied Physics |
| ATC | Active Thermal Cooling |
| ATC | Automatic Temperature Conversion |