| Abbreviation | Definition |
|---|---|
| ANN | Ammonia Nitrite Nitrate |
| ANS | 1-Anilino-8-Naftalen-Sulfonat |
| AO | Agent Orange (Toxic) |
| AO | Aldehyde Oxidase |
| AO | Aqueous Oxygen |
| AO | Atomic Orbital |
| AOA | Anhydrous Oripavine Alkaloid |
| AOAA | Amino-oxy-acetic Acid (biochemistry) |
| AOAA | Application of Aminooxyacetic Acid |
| AOCG | Applied Organic Chemistry Group |
| AOCS | American Oil Chemists Society |
| AOD | Argon Oxygen Decarburisation |
| AOD | Argon Oxygen Decarburization |
| AOE | Amino Oxo Epoxidecanoic |
| AOI | Age Of Innocence |
| AORC | Association of Official Racing Chemists |
| AORP | Advanced Oxidation/Reduction Process |
| AP | Anticorrosive Paint |
| AP | Archimedes Plutonium |
| APACE | Asia Pacific Association of Chemical Ecologists |