| AABC | Australian Associated Bonsai Clubs | |
| AACC | Avicultural Advancement Council of Canada | |
| AB | Apple Blossom | |
| ABA | African Bonsai Association | |
| ABA | ABscissic Acid | |
| ABA | Abscisic Acid | |
| ABC | American Botanical Council | |
| ABCD | Access to Biological Collections Data | |
| ABCP | African Blackwood Conservation Project | |
| ABE | Anomalous Biological Entity | |
| ABF | Activated Biofilter | |
| ABG | Atlanta Botanical Gardens | |
| ABIS | Andean Botanical Information System | |
| ABLO | Australian Botanical Liaison Officer | |
| ABLS | American Bryological and Lichenological Society | |
| ABRS | Australian Biological Resources Study | |
| ABS | American Bryological Society | |
| ABS | American Begonia Society | |
| ABS | American Bonsai Society | |
| ACA | American Chichlid Association | |
| ACCP | Accelerated Canopy Chemistry Program | |
| ACGH | Array Comparative Genomic Hybridization | |
| ACGM | Advisory Committee for Genetic Modification | |
| ACMV | African Cassava Mosaic Virus | |
| ACNP | Audubon Center for Native Plants | |
