| AA | Alcoholics Anonymous - a service organization. |
| AAFI | Amateur Athletics Federation of India |
| AAGSP | All Assam Gana Sangram Parishad |
| AARRP | Afro Asian Rural Reconstruction Progreamme. |
| ABC | Atomic, Biological and Chemical (warfare),Audit Bureau of Circulation. |
| AC | Ante Christum (Before Christ), Alternating Current, Ashok Chakra, Air Conditioner |
| ABM | Anti Ballistic Missile |
| ABU | Asian Broadcasting Union |
| ACC | Auxiliary Cadet Corps |
| AD | Anna Domini (After Christ) |
| ADAM | Animated Dissection |
| ADB | Asian Development Bank |
| ADF | African Development Fund |
| ADC | Aide de Camp (Assistant to Governors) |
| AIADMK | All India Anna Dravida Munnetra Kazhagam |
| AEC | Atomic Energy Commission |
| AFC | Asian Football Confederation |
| AG | Accountant General, Adjutant General |
| AH | Anna Hegirae (Prophet Muhammad's flight from Mecca to Medina 622 AD) |
| AFPRO | Action for Food Programme. |
| AI | Artificial Intelligence, Air India |
| AGSOC | Asian Games Special Organising Committee |
| AICTE | All India Council for Technical Education |
| AIDS | Acquired Immuno Deficiency Syndrome. |
| AIFF | All India Football Federation |
| AIFACS | All India Fine Arts and Crafts Society |
| AIIMS | All India Institute of Medical Science |
| AIML | All India Muslim League |
| AITUC | All India Trade Union Congress |
| AISSF | All India Sikh Students' Federation. |
| AIREC | All India Railway Employees Confederation. |
| AIWC | All India Women's Conference. |
| AICC | All India Congress Committee |
| AIBEU | All India Bank Employees' Union |
| AICTU | All India Communist Trade Union |
| AM | Anti-meridian (Before Noon), Amplitude Modulation. |
| AMIE | Associate Member of the Insitution of Engineers. |
| AMC | Army Medical Corps |
| ABC | American/Australian Broadcasting Corporation |
| ANC | African National Congress |
| AOC | Air Officer Commanding. |
| ANERT | Agency for Non-conventional Energy and Rural Technology. |
| ALH | Advanced Light Helicopter |
| APPLE | Ariane Passenger Pay Load Experiment |
| ANN | Artificial Neutral Network |
| ANZUS | Australia, New Zealand and US Pacific Pact Nations. |
| APCTT | Asian and Pacific Centre for Transfer of Technology. |
| APD | Automated Peritoneal Dialysis |
| APEC | Asia Pacific Economic Cooperation. |
| APM | Administered Price Mechanism. |
| ARC | Administrative Reforms Commission. |
| ARDC | Agricultural Refinance and Development Corporation. |
| ART | Assisted Reproductive Technologies |
| ASC | Army Service Corps |
| ASEAN | Association of South East Asian Nations. |
| ASAP | As Soon As Possible |
| ASCII | American Standard Code for Information Interchange. |
| ASBD | Anti Social Behaviour Disorder |
| ASLV | Augmented Satellite Launch Vehicle |
| ASPAC | Asian and Pacific Council |
| ASSOCHAM | Associated Chamber of Commerce and Industry |
| ATGM | Anti Tank Guided Missile |
| AT & T | American Telegraphic & Telephone Co.Ltd., |
| ATC | Air Traffic Control. |
| ATS | Anti Tetanus Serum |
| ATM | Automated Teller Machine |
| ATV | Advanced Technology Vessel. |
| AVSM | Ati Vishist Seva Medal. |
| AU | Astronomical Unit, African Union |
| AWACS | Airborne Warning and Control System |
| AAASI | Academy of Archaeology and Ancient Sciences of India. |
| AAI | Airport Authority of India Ltd., |
| APO | Army Post Office |
| AIRF | All India Railwaymen's Federation. |
| ASL | Advanced System Laboratory; Above Sea Level. |
| ANZAC | Australian and New Zealand Army Corps. |
| ALEAP | Association of Lady Entrepreneurs of Andhra Pradesh |
| APC | Armoured Personnel Carrier |
| ADU | Ambedkar University, Delhi. |
| ACTA | Anti-counterfeiting Trade Agreement. |
| AQI | Air Quality Index |
| ASBA | Application Supported by Blocked Amounts. |
| AURA | Autonomous Unmanned Research Aircraft. |
| AERB | Atomic Energy Regulatory Board |