| Abbreviation | Definition |
|---|---|
| APSI | Advanced Placement Summer Institute |
| APSI | Advanced Placement Summer Institutes |
| APSI | AP Summer Institute |
| APSI | Asian Pacific Studies Institute |
| AQI | Anesthesia Quality Institute |
| ARCI | American Railway Car Institute |
| ARCI | Avian Research and Conservation Institute |
| ARI | AIDS Research Institute |
| ARI | Angus Reid Institute |
| ARI | Autism Research Institute |
| ARI | Ayn Rand Institute |
| ARIAH | Association of Research Institutes in Art History |
| ARICS | Associate Royal Institution of Chartered Surveyors |
| ARIJ | Applied Research Institute-Jerusalem |
| ARISC | American Research Institute of the |
| ARISC | American Research Institute of the South Caucasus |
| ARISE | Advanced Research Institute of Science and Engineering |
| ARLI | Action Research Leaiership Institute |
| ARLI | Aspiring Radical Leaders Institute |
| ARRI | Aquatic Restoration and Research Institute |