| Abbreviation | Definition |
|---|---|
| 5S | Sifting, Sorting, Sweeping, Standardizing, Sustaining |
| A | Albino guinea pig |
| A/b | antibody |
| A/G | albumin-to-globulin |
| A² | amyloid-² |
| AAA | A trial of Aspirin Against no Aspirin |
| AAAAA | AHo's Amazing Atlas of Antibody Anatomy |
| AAALAC | Association for Assessment and Accreditation for Laboratory Animal Care |
| AAALAC | Association for Assessment and Accreditation of Laboratory Animal Care |
| AABB | American Association of Blood Banks |
| AAHL | Aquatic Animal Health Laboratory |
| AAL | Applied Anthropology Laboratories |
| AAMPS | Amino Acid and Metabolizable Protein System |
| AAMX | Aceto Acet M Xylidine |
| AANL | A Alikhanyan National Laboratory |
| AANL | Artem Alikhanian National Laboratory |
| AANL | Artem Alikhanyan National Laboratory |
| AAR | AST / ALT Ratio |
| AARL | Abilene AI and Robotics Laboratory |
| AARL | Aeronautical and Astronautical Research Laboratory |