| Abbreviation | Definition |
|---|---|
| AOPA | American Orthotic & Prosthetic Association |
| AOPA | American Orthotic and Prosthetic Association |
| AOPA | Australian Orthotic Prosthetic Association Inc. |
| AOS | American Orchid Society |
| AOTA | American Occupational Therapy Association |
| AOTPAC | American Occupational Therapy Association, Inc. Political Action Committee |
| AOU | American Ornithologists Union |
| APA | Alaska Packers Association |
| APA | Allied Professional Association |
| APA | Amateur Publication Association |
| APA | American Parquet Association |
| APA | American Payroll Association |
| APA | American Planning Association |
| APA | American Plywood Association |
| APA | American Psychiatric Association |
| APA | American Psychoanalytic Association |
| APA | American Psychology Association |
| APA | American Psyciatric Association |
| APA | Architectural Precast Association |
| APA | Association of Paper Archivists |