| Acronym | Definition |
|---|
| ARI | Ayn Rand Institute |
| ARI | Air-Conditioning and Refrigeration Institute |
| ARI | Autism Research Institute |
| ARI | Asia Research Institute |
| ARI | Acute Respiratory Infection |
| ARI | Aberdeen Royal Infirmary |
| ARI | Army Research Institute |
| ARI | American Railcar Industries (St. Louis, MO) |
| ARI | Applied Research Institute (various locations) |
| ARI | Air Routing International (Rockwell Collins; Iowa) |
| ARI | Acute Respiratory Illness |
| ARI | Alcohol Related Injury |
| ARI | Arden Realty, Inc. |
| ARI | Arthur Rylah Institute (ecological research institute; Victoria, Australia) |
| ARI | Aaron Rents, Inc. (various locations) |
| ARI | Advisory Research, Inc. (various locations) |
| ARI | Artist Run Initiative (various locations) |
| ARI | Automotive Resources International |
| ARI | Agricultural Research Institute |
| ARI | Action Research International (online journal) |
| ARI | Alarm Relay Interface |
| ARI | Address Recognized Indicator |
| ARI | Aspect Ratio Information |
| ARI | Absolute Risk Increase |
| ARI | Australian Rivers Institute (Griffith University; Australia) |
| ARI | Aderans Research Institute (hair regeneration; Georgia) |
| ARI | Acquisition Reform Initiative (US DoD) |
| ARI | Appareil Respiratoire Isolant (French: Breathing Apparatus) |
| ARI | African Rehabilitation Institute |
| ARI | Average Recurrence Interval |
| ARI | Arthritis and Rheumatism International |
| ARI | Autoridad de la Región Interoceánica (Inter-Oceanic Authority) |
| ARI | Adrenergic Reuptake Inhibitor (psychopharmacology) |
| ARI | Advanced Research Institute |
| ARI | Adsorption Research, Inc. (Dublin, OH) |
| ARI | Andean Regional Initiative |
| ARI | Access to Radiology Information (Integrating the Healthcare Enterprise) |
| ARI | Aldose Reductase Inhibitor |
| ARI | Afirmación para una República Igualitaria (Spanish; Argentina) |
| ARI | Achaemenid Royal Inscriptions (archaeology) |
| ARI | Allotments Regeneration Initiative (UK) |
| ARI | Agence Régionale de l'Innovation (French: Regional Innovation Agency) |
| ARI | Annual Risk of Infection |
| ARI | Archaeological Research Institute |
| ARI | Adelaide Research & Innovation Pty Ltd. (Australia) |
| ARI | Azimuthal Resistivity Image (energy production) |
| ARI | Alcohol Related Incident |
| ARI | Autofahrer-Rundfunk-Information |
| ARI | Airpower Research Institute |
| ARI | Auto Recyclers, Inc. (various locations) |
| ARI | Association Régionale pour l'Intégration (French: Association for Regional Integration; Marseille, France) |
| ARI | Alexandria Research Institute (Alexandria, Virginia; Virginia Tech) |
| ARI | American Refrigerant Institute (now Air Conditioning, Heating and Refrigeration Institute) |
| ARI | Accelerated Research Initiative |
| ARI | Acute Renal Insufficiency |
| ARI | Applied Research Inc. |
| ARI | All Risk Insurance |
| ARI | ANSTO Radiopharmaceuticals and Industrials (Australia) |
| ARI | Acute Respiratory Insufficiency |
| ARI | Arica, Chile - Chacalluta (Airport Code) |
| ARI | annual recurrence interval (hydrology) |
| ARI | Aileron Rudder Interconnect |
| ARI | Astoria Mini Mart (Amtrak station code; Astoria, OR) |
| ARI | American Remanufacturers, Inc. |
| ARI | Acoustics Research Institute |
| ARI | Automatic Return Item |
| ARI | Aviation Restructure Initiative |
| ARI | Alternate Rod Insertion |
| ARI | Associazione Rebussistica Italiana (Italian Rebus Association) |
| ARI | Accounting Rate of Interest |
| ARI | Automatic Room Identification |
| ARI | Audience Research Institute |
| ARI | Assistant de Recherche d'Informations sur Internet (French: Research Assistant of Information on the Internet; research software) |
| ARI | Automatic Reset Induction (US Army) |
| ARI | Agrarian Reform Institute |
| ARI | Address Recognized Indicator Bit |
| ARI | Aquifer Risk Index |
| ARI | Agatston Research Institute (Miami Beach, FL, USA) |
| ARI | Asia Rural Institute (Japan) |
| ARI | Aileron to Rudder Interconnect |
| ARI | Activity Routing Identifier |
| ARI | Associazione Radiamatori Italiani (Italian Ham Radio Association) |
| ARI | Affordable Readiness Initiative |
| ARI | Attitude Reference Indicator |
| ARI | ATS R&D IPT |
| ARI | Abbey Road Interactive Studios (London, England) |
| ARI | Automatic Rudder Interconnect |
| ARI | Atelier de Ressources Informatiques (French: Computer Resources Workshop; est. 2003) |
| ARI | Addressee Routing Indicator |
| ARI | Armrest Rotary Input |
| ARI | Actuarial Removal Interval |
| ARI | Advanced Rigid Insulation |
| ARI | Automatic Railway Information |