| ABS | Anti-lock Braking System |
| APJ Abdul Kalam | Avul Pakir Jainulabdeen Abdul Kalam |
| ASAP | As Soon As Possible |
| ADB | Asian Development Bank |
| ATM | Automated Teller Machine |
| AICTE | All India Council for Technical Education |
| AMIE | Associate Member of the Institution of Engineers |
| ASR | Automated Speech Recognition |
| ACD | Automatic Call Distributor |
| ABG | Arterial Blood Gas |
| ACS | American Chemical Society |
| ADHD | Attention Deficit Hyperactivity Disorder |
| AIDS | Acquired Immune Deficiency Syndrome |
| ALS | Amyotrophic Lateral Sclerosis |
| ARDS | Acute Respiratory Distress Syndrome |
| AJAX | Asynchronous JavaScript and XML |
| API | Application Programming Interface |
| AD | Anno Domini |
| AM and PM | Anti Meridiem and Post Meridiem |
| AAI | Airport Authority of India |
| ABP News | Ananda Baazar Patrika News |
| ACC | Associated Cement Companies |
| ACS | American Chemical Society |
| ADIDAS | Adolf "Adi" Dassler |
| AHRC | Asian Human Rights Commission |
| AIAAA | American Institute of Aeronautics and Astronautics |
| AMC | Annual Maintenance Contract |
| AMC | American Motors Corporation |
| AMUL | Anand Milk Union Limited |
| AMW | Asian Motors Works Limited |
| AT&T | American Telephone & Telegraph Company |
| AYUSH | Ayurvedic, Yoga, and Naturopathy, Unani, Siddha, and Homeopathy |
| AFAIK | As far as I know |
| APK | Android Application Package |
| ASCII | American Standard Code for Information Interchange |
| ASP | Active Server Page |
| ASP | Application Service Provider |
| ATA or PATA | Advanced Technology Attachment / Parallel Advanced Technology Attachment |
| ASAP | As Soon As Possible |
| ABVP | Akhil Bharatiya Vidyarthi Parishad |
| AKA | Also Known As |
| AMA | Ask Me Anything |
| AFK | Away From Keyboard |
| AML | Acute Myeloid Leukemia |
| ASAT | Anti-satellite Weapons |
| ASLV | Augmented Satellite Launch Vehicle / Advanced Satellite Launch Vehicle |
| AFCAT | Air Force Common Admission Test |
| ANM | Auxiliary Nurse Midwife |
| ASEAN | Association of Southeast Asian Nations |
| ATS | Application Tracking System |
| AMA | Ask Me Anything |
| AAMOF | As a Matter of Fact |
| AFAIR | As far as I remember / recall |
| AIIMS | All India Institute of Medical Science |
| APTET | Andhra Pradesh Teacher Eligibility Test |
| ACL | Anterior Cruciate Ligament |
| ARF | Acute Kidney Failure |
| ARDS | Acute Respiratory Distress Syndrome |
| A Time Zone | Alpha Time Zone (Military Time) |
| ACDT Time Zone | Australian Central Daylight Time |
| ACST Time Zone | Australian Central Standard Time (Standard Time) |
| ACT Time Zone | Acre Time (Standard Time) |
| ACT Time Zone | Australian Central Time |
| ACWST Time Zone | Australian Central Western Standard Time (Standard Time) |
| ADT Time Zone | Arabia Daylight Time (Daylight Saving Time) |
| ADT Time Zone | Atlantic Daylight Time / Atlantic Daylight Saving Time (Daylight Saving Time) |
| AEDT Time Zone | Australian Eastern Daylight Time (Daylight Saving Time) |
| AEST Time Zone | Australian Eastern Standard Time / Eastern Standard Time (Standard Time) |
| AET Time Zone | Australian Eastern Time |
| AFT Time Zone | Afghanistan Time (Standard Time) |
| AKDT Time Zone | Alaska Daylight Time (Daylight Saving Time) |
| AKST Time Zone | Alaska Standard Time (Standard Time) |
| ALMT Time Zone | Alma-Ata Time (Standard Time) |
| AMST Time Zone | Amazon Summer Time (Daylight Saving Time) |
| AMST Time Zone | Armenia Summer Time (Daylight Saving Time) |
| AMT Time Zone | Amazon Time (Standard Time) |
| AMT Time Zone | Armenia Time (Standard Time) |
| ANAST Time Zone | Anadyr Summer Time (Daylight Saving Time) |
| ANAT Time Zone | nadyr Time (Standard Time) |
| AQTT Time Zone | Aqtobe Time (Standard Time) |
| ART Time Zone | Argentina Time (Standard Time) |
| AST Time Zone | Arabia Standard Time (Standard Time) |
| AST Time Zone | Atlantic Standard Time / Atlantic Time (Standard Time) |
| AT Time Zone | Atlantic Time |
| AWDT Time Zone | Australian Western Daylight Time (Daylight Saving Time) |
| AWST Time Zone | Australian Western Standard Time / Western Standard Time (Standard Time) |
| AZOST Time Zone | Azores Summer Time (Daylight Saving Time) |
| AZOT Time Zone | Azores Time (Standard Time) |
| AZST Time Zone | Azerbaijan Summer Time (Daylight Saving Time) |
| AOE Time Zone | Anywhere on Earth (Standard Time) |
