A Aftermath
AA Affirmative Action committee
AA Alcoholics Anonymous
AA Antiaircraft Artillery
AA Associate in Accounting
A&A Astronomy and Astrophysics (Espacial)
AA Automobile Association (Inglaterra)
AAA American Automobile Association
AAAL American Academy of Arts and Letters
AAAS American Association for the Advancement of Science
AAII American Association of Individual Investors
AAMSI American Association for Medical Systems Informatics
AAO Anglo-Australian Observatory (Espacial)
AAP Affirmative Action Program
AARC Anglo-American Cataloging Rules
AARN Australian Academic Research Network (Networking)
AARP American Association of Retired Persons
AAS American Astronomical Society (Espacial)
AAVSO American Association of Variable Star Observers (Espacial)
AB ABle seaman
ABA American Bar Association
ABA American Basketball Association
ABA American Booksellers Association
ABBR ABBReviation
ABC American Broadcasting Company (nome de companhia)
AC Alternating Current (ac, veja também DC)
AC Ante Christum (Antes de Cristo)
AC Ante Cibum (antes de comidas)
ACAA Agricultural Conservation and Adjustment Administration
ACAWS Advisory, Caution, And Warning System
ACBL American Contract Bridge League
ACC Argonne Code Center
ACCS Army Command and Control System
ACD Automatic Call Distributor (Telefonia)
ACE Advanced Composition Explorer (Espacial)
ACE Advanced Computing Environments (nome de companhia)
ACE Automatic Calibration and Equalization
ACHEFT Automated ClearingHouse Electronic Funds Transfer
ACK ACKnowledge
ACL Advanced Cmos Logic
ACLU American Civil Liberties Union
ACM Association for Computing Machinery
ACRV Assured Crew Return Vehicle (ou) Astronaut Crew Rescue Vehicle (Espacial)
ACS Advanced Communications System
ACSE Association Control Service Entity (ISO/CCITT layer 7)
ACT Action for Children's Television (em Cambridge, MA)
ACT American Conservatory Theater
ACTS Advanced Communications Technology Satellite
ACTS Automatic Coin Telephone Service (Telefonia)
ACU Alarm Control Unit
ACU Automatic Call Unit (Telefonia)
ACW Alternating Continuous Waves
AD After Date
A/D Analog to Digital converter (veja também ADC)
AD Anno Domini (em o ano do nosso Senhor)
AD Application Development
Ad Astra To the stars [Latin, Espaço]
ADAP Alzheimer's disease-associated protein
ADAP American Discount Auto Parts (nome de companhia)
ADB A DeBugger
ADB Apple Desktop Bus
ADC Analog to Digital Converter
ADCI Automatic Display Call Indicator 
AD&D Advanced Dungeons & Dragons
ADF Automatic Direction Finder
ADM ADMiral
ADP Adenosine Di-Phosphate
ADP Administrative Data Processing
ADP Advanced Data Processing
ADPCM Pulse Code Modulation with Adaptive Quantization
ADS Application Development System
ADSR Attack Decay Sustain Release
ADT Abstract Data Type
ADT Atlantic Daylight Time
AE Application Execution
AEA American Electronics Association
AEC Atomic Energy Commission
AEF American Expeditionary Force (veja também BEF)
AEGIS Advanced Electronic Guidance and Instrumentation System
AF Adventures in Fantasy
AF Air Force
AF Audio Frequency
AFADS Automatic Force Adjustment Data System 
AFATDS Advanced Field Artillery Tactical Data System
AFB Air Force Base
AFC American Football Conference
AFC Automatic Flight Control
AFC Automatic Frequency Control
AFCAC Air Force Computer Acquisition Center
AFCC Air Force Communications Command
AFGE American Federation of Government Employees
AFIPS American Federation of Information Processing Societies
AFL American Federation of Labor
AFL American Football League
AFLCIO American Federation of Labor and Congress of Industrial Organizations
AFNOR Association Francaise de NORmalization
AFP Appletalk Filing Protocol
AFS Andrew File System
AFSC Air Force Systems Command
AFSCME American Federation of State, County and Municipal Employees
AFTRA American Federation of Television and Radio Artists
AG Adjutant General
AG Arcade Game
AG Attorney General
AGCT Army General Classification Test
AGN Active Galactic Nucleus (Espacial)
AHL American Hockey League
AHQ Air HeadQuarters
AI Artificial Intelligence
AIAA American Institute of Aeronautics and Astronautics (Espacial)
AIC Automatic Intercept Center 
AID Agency for International Development
AIDDE Ames' Interactive Dynamic Display Editor
AIDS Acquired ImmunoDeficiency Syndrome
AIOD Automatic Identification Outward Dialing 
AIS Automatic Intercept System
AIX Advanced Interactive eXecutive (nome da IBM para UNIX)
AJ Astronomical Journal (Espacial)
AK Alaska
AKA Also Known As
AL Alabama (designação postal para estado americano)
AL American League (baseball)
ALA American Library Association
ALA Automobile Legal Association
ALBM Air-to-Land Ballistic Missile
ALC Automatic Load Control
ALGOL ALGOrithmic Language
ALIT Automatic Line Insulation Testing (Telefonia)
ALPO Association of Lunar and Planetary Observers (Espacial)
ALS Advanced Launch System (Espacial)
ALU Arithmetic Logic Unit
A&M Agricultural and Mechanical
AM Amplitude Modulation
AM Ante Meridiem (before noon)
AMA American Medical Association
AMA Automatic Message Accounting (Telefonia)
AMARC Automatic Message Accounting Recording Center 
AMBA Association of Master of Business Administration
AMC Albany Medical College
AMC American Motors Corporation(?) (nome de companhia)
AMC Appalachian Mountain Club
AMD Advanced Micro Devices (nome de companhia)
AMEX AMerican EXpress (nome de companhia)
AMI Alternate Mark Inversion (veja também NRZ, NRZI, B8ZS)
AMORC Ancient Mystic Order Rosae Crucis
AMP Adenosine MonoPhosphate
AMPAS Academy of Motion Picture Arts and Sciences
AMPAS Acedemy of Motion Picture Arts and Sciences
AMRAAM Advanced Medium Range Air-To-Air Missile
AMROC American Rocket Company (Espacial)
AMSAT radio AMateur SATellite corp.
AMU Atomic Mass Unit
AMVET AMerican VETeran
ANA American Nurses Association
ANAC Automatic Number Announcemnt Circuit (Telefonia)
ANC All Number Calling (Telefonia)
ANC Army Nurse Corps
ANDF Architecture-Neural Distribution Format
ANF Automatic Number Forwarding (Telefonia)
ANG Air National Guard
ANI Automatic Number Identification (veja também: CLID) (Telefonia)
ANL Argonne National Laboratory
ANOVA ANalysis Of VAriance
ANPA American Newspaper Publishers Association
ANSI American National Standards Institute
ANZUS Australia, New Zealand, United States
AO Account Of
AOA Abort Once Around [NASA, Lançamento]
AOA Abort Once Around (Espacial)
AOL Absent Over Leave (veja também AWOL)
AOS Academic Operating System
AOS Alternate Operator Service (Telefonia)
A/P Accounts Payable
AP Additional Premium
AP All Points
AP Associated Press (nome de companhia)
APA All Points Addressable
APA American Psychological Association
APB All Points Bulletin
APDA Apple Programmers and Developers Association
API Application Programming Interface
APICS American Production and Inventory Control Society
Ap.J Astrophysical Journal (Espacial)
APL A Programming Language
APL acute promyelocytic leukemia (infecção)
APO Alpha Phi Omega, service fraternity
APO Army Post Office
APP Applications Portability Profile
APPC Advanced Peer-to-Peer Communications
APR Annual Percentage Rate 
APSE Ada Programming Support Environment
APU Auxiliary Power Unit (Espacial)
AQ Accumulator-Quotient register
A/R Accounts Receivable
AR Address Register
AR Arkansas
ARC AIDS-related complex
ARC American Red Cross
ARC Ames Research Center (NASA) (Espacial)
ARCNET Attached Resource Computer local area NETwork
ARO After Receipt of Order
ARP Address Resolution Protocol
ARPA Advanced Research Projects Agency (do DoD, veja também DARPA)
ARPANET ARPA (q.v.) NETwork
ARRL Amateur Radio Relay League
ARV American Revised Version
AS Anglo-Saxon
ASA Acetyl Salicylic Acid
ASAP As Soon As Possible
ASC Accredited Standards Committee
ASCAP American Society of Composers, Authors, and Publishers
ASCC Automatic Sequence-Controlled Calculator
ASCII American Standard Code for Information Interchange
ASDIC Anti-Submarine Detection Investigation Committee 
ASDSP Application-Specific Digital Signal Processor
ASG Automated Sciences Group
ASHRAE Amer. Soc. of Heating, Refrigerating and Air-cond. Engineers, inc.
ASIC Application Specific Integrated Circuit
ASME American Society of Mechanical Engineers
ASN Abstract Syntax Notation One (ISO/CCITT ASN.1)
ASP Aggregated Switch Procurement
ASRM Advanced Solid Rocket Motor (Espacial)
ASSR Autonomous Soviet Socialist Republic
AST Atlantic Standard Time
ASV American Standard Version
AT Atlantic Time
ATA Automatic Trouble Analysis 
ATACC Advanced Tactical Air Command Central
ATB Advanced Technology Bomber 
ATC Air Traffic Control
ATDRS Advanced Tracking and Data Relay Satellite (Espacial)
ATF Advanced Technology Fighter
ATIS Atherton Tools Interface Specification
ATLAS Atmospheric Laboratory for Applications and Science (Espacial)
ATM Amateur Telescope Maker (Espacial)
ATM Asynchronous Transfer Mode
ATM Automatic Teller Machine
ATO Abort To Orbit [NASA, Lançamento]
ATO Abort To Orbit (Espacial)
ATOMS AT&t Optimized Materials Simulator
ATP Adenosine TriPhosphate
ATPCO Airline Tariff Publishing COmpany
AT&T American Telephone & Telegraph (nome de companhia)
ATT American Telephone & Telegraph (nomalmente escrito AT&T quando separado)
ATTIS American Telephone and Telegraph Information Systems [AT&T] 
ATV All Terrain Vehicle
AU Astronomical Unit (93.000.000 milhas) (Espacial)
AU Astronomical Unit (Espacial)
AUI Attachment Universal Interface
AURA Association of Universities for Research in Astronomy (Espacial)
AUS Army of the United States
AUTODIN AUTOmatic DIgital Network
AUTOVON  AUTOmatic VOice Network
AV AudioVisual
AVLIS Atomic Vapor Laser Isotope Separation
AWACS Airborne Warnings And Control Systems
AWEA American Wind Energy Association
AWK al Aho, peter Weinberger, brian Kernighan (padrão de linguagem)
AWOL Absent WithOut Leave (veja também AOL)
AW&ST Aviation Week and Space Technology (a.k.a. AvLeak) (Espacial)
AXAF Advanced X-ray Astrophysics Facility (Espacial)
AZ Arizona
® Pesquisa RXA