| AAI | Airport Authority of India |
| ABG | Arterial Blood Gas |
| ABP | Ananda Bazaar Patrika News |
| ABM | Anti Balistic Missile |
| ABS | Anti-lock Braking System |
| ACD | Automatic Call Distributor |
| ACC | Associated Cement Companies |
| ACS | American Chemical Society |
| ACU | Asian Currency Union |
| AD | Anno Domini |
| ADB | Asian Development Bank |
| ADIDAS | Adolf "Adi" Dassler |
| ADHD | Attention Deficit Hyperactivity Disorder |
| ADR | American Depository Receipt |
| AHRC | Asian Human Rights Commission |
| AIAAA | American Institute of Aeronautics and Astronautics |
| AICTE | All India Council for Technical Education |
| AIDS | Acquired Immune Deficiency Syndrome |
| AJAX | Asynchronous JavaScript and XML |
| ALS | Amyotrophic Lateral Sclerosis |
| AMC | Annual Maintenance Contract, American Motors Corporation |
| AMIE | Associate Member of the Institution of Engineers |
| AML | Acute Myeloid Leukemia |
| AMUL | Anand Milk Union Limited |
| AMW | Asian Motors Limited |
| API | Application Programming Interface |
| APJ Abdul Kalam | Avul Pakir Jainulabdeen Abdul Kalam |
| APK | Android Application Package |
| ARMD | Age Related Macular Degeneration |
| ARDS | Acute Respiratory Distress Syndrome |
| ASAP | As Soon As Possible |
| ASAT | Anti-satellite weapons |
| ASCII | American Standard Code for Information Interchange |
| ASEAN | Association of Southeast Asian Nations |
| ASLV | Augmented Satellite Launch Vehicle |
| ASP | Active Server Page |
| ASR | Automated Speech Recognition |
| ATA | Advanced Technology Attachment |
| AT&T | American Telephone & Telegraph Company |
| ATM | Automated Teller Machine |
| ATS | Anti-Terrorism Squad |
| AWACS | Airborne Warning and Control System |
| AYUSH | Ayurvedic, Yoga and Naturopathy, Unani, Siddha and Homeopathy |
| AM and PM | AM: Anti Meridiem, PM: Post Meridiem |
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