(Main list of acronyms)
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- I – (s) Iodine – One (in Roman numerals)
I0–9
- I<sup>2</sup>C or I-squared-C - (i) Inter-Integrated Circuit
- I2WD or I<sup>2</sup>WD – (i) U.S. Intelligence and Information Warfare Directorate (CERDEC)
IA
- ia – (s) Interlingua language (ISO 639-1 code)
- IA – (s) Iowa (postal symbol)
- IAAF – (i) International Association of Athletics Federations ("International Amateur Athletics Federation" from 1912 to 2001; renamed "World Athletics" in 2019)
- IAAL – (i) I Am A Lawyer
- IAAS - (p) Infrastructure-as-a-Service
- IAB –
- (i) International Association for Biologicals
- IATA code of McConnell Air Force Base
- IACREOT – (i) International Association of Clerks, Recorders, Election Officials, and Treasurers
- IAD –
- (i) Ion Assisted Deposition
- IATA code for Washington Dulles International Airport
- IADS – (i) Integrated Air Defence System
- IAE - (i) International Aero Engines (aircraft engine joint venture)
- IAEA – (i) International Atomic Energy Agency
- IAF
- {i} Industrial Areas Foundation
- (i) Israeli Air Force
- IAFG – (i) Information Assurance Focus Group
- IAI –
- (i) International African Institute
- Israel Aircraft Industries
- IANA – (i) Internet Assigned Numbers Authority
- IANAL – (i) I Am Not A Lawyer
- IAPD
- International Associates of Paediatric(sic) Dentistry
- (i) Investment Adviser Public Disclosure
- iShares Asia Pacific Dividend
- IAQ – (i) Indoor air quality – Infrequently Asked Questions
- IAS – (i) Image Assessment System
- IASIP – (i) It's Always Sunny in Philadelphia
- IATA – (a/i) International Air Transport Association
- IATF – International Automotive Task Force
- IATSE – International Alliance of Theatrical Stage Employees
- IAU – (i) International Association of Universities – International Astronomical Union
- IAUC – (i) International Astronomical Union Circular
- IAW – (i) In Accordance With
IB
- IB – (i) International Baccalaureate
- IBA – (i) Important Bird Area
- IBD – (i) Inflammatory Bowel Disease
- IBDM – (i) Information Based Decision Making
- IBDS – (i) Integrated Biological Detection System – International Business Development Specialist
- IBF - International Boxing Federation
- IBGe – (i) Isobutylgermane
- IBGE – (i) Instituto Brasileiro de Geografia e Estatística (Portuguese, "Brazilian Institute of Geography and Statistics")
- IBHOF - International Boxing Hall of Fame
- IBM – (i) International Business Machines
- ibo – (s) Igbo language (ISO 639-2 code)
- IBRD – (i) International Bank for Reconstruction and Development (part of the World Bank)
- IBS – (i) Irritable Bowel Syndrome
IC
- IC
- (s) Ice Crystals (METAR Code)
- Iceland (FIPS 10-4 country code)
- (i) Integrated Circuit - [inner circle]
- ICANN – (a) Internet Corporation for Assigned Names and Numbers
- ICAO – (i) International Civil Aviation Organization
- ICBM – (i) Intercontinental Ballistic Missile
- ICBM – I see (phonetically "c") BatMan
- ICBN – (i) International Code of Botanical Nomenclature
- ICC
- (i) Integrated Command and Control
- International Criminal Court
- International Cricket Council
- Interstate Commerce Commission
- International Chamber of Commerce
- ICD
- (i) Implantable Cardioverter-Defibrillator
- Initial Capabilities Document
- International Classification of Diseases
- ICE
- (i/a) (U.S.) Immigration and Customs Enforcement
- In case of emergency
- Internal Combustion Engine (Vehicles)
- ICES – (a/i) International Council for the Exploration of the Sea
- ICF – (i) Intelligent Community Forum
- ICHTHYS – (a) Iesous Christos, Theou Yios, Soter (Greek, "Jesus Christ, Son of God, Savior")
- ICM
- (i) Improved Conventional Munition
- Integrated Collection Management
- International Congress of Mathematicians
- Iraq Campaign Medal
- ICMP – (i) Internet Control Message Protocol
- ICNAF – (i) International Commission for the Northwest Atlantic Fisheries (became NAFO in 1978)
- ICNI – (i) Integrated Communication, Navigation, and Identification
- ICO – (i) Intermediate Circular Orbit
- ICP
- (i) Inductively coupled plasma
- Insane Clown Posse
- ICPE – (a/i) International Conference on Pharmacoepidemiology, the annual conference of the International Society for Pharmacoepidemiology
- ICRAF – (i) International Centre for Research in Agroforestry (a.k.a. World Agroforestry Centre since 2002)
- ICRISAT – (i/a) International Crops Research Institute for the Semi-Arid Tropics
- ICRL – (i) Individual Component Repair List
- ICRS – (i) International Celestial Reference System
- ICS
- (i) In-Country Support
- Intelligence and Communications Systems
- Interim Contractor Support
- ICSI – (p) Intracytoplasmic Sperm Injection
- ICT – (i) Information and communication technologies
- ICTH – (i) Island Closest to Heaven/Hell Final Fantasy VIII
- ICV – (i) Infantry Carrier Vehicle
- ICW
- (i) In Co-ordination With
- Indonesia Corruption Watch
- Infectious and Chemotherapeutic Waste
- Insulating Concrete Wall
- Integral Crystalline Waterproofing
- (p) Interactive Courseware
- (i) International Championship Wrestling (defunct US professional wrestling promotion)
- ICYMI – (i) In Case You Missed It
- ICZN
- (i) International Code of Zoological Nomenclature
- International Commission on Zoological Nomenclature
ID
- id – (s) Indonesian language (ISO 639-1 code)
- ID
- (s) Idaho (postal symbol)
- (p) Identity
- (s) Indonesia (FIPS 10-4 country code; ISO 3166 digram)
- (i) Infantry Division
- Intelligent Design
- ID10T Error – (i) Idiot User Error (IT help desk inside joke)
- IDA
- (i) U.S. Institute for Defense Analyses
- International Development Association (part of the World Bank
- IDC – (i)
- International Data Corporation
- "I Don't Care"
- IDDI – (i) I don't do initialisms (see irony)
- IDE
- (i) Integrated Development Environment
- Integrated Drive Electronics
- IDeA – (a) Improvement and Development Agency, the former name of Local Government Improvement and Development in the United Kingdom
- IDEA
- (a) Individuals with Disabilities Education Act (U.S.)
- International Data Encryption Algorithm
- International Design Excellence Awards
- IDF
- (i) Israel Defense Forces
- Intel Development Forum
- International Dairy Federation
- IDGAF – (i) I don't give a f**k
- IDK – (i) I don't know
- IDKIBTI – I don't know, I'm black, that's it
- IDL – (i) Interface Definition Language
- IDN – (s) Indonesia (ISO 3166 trigram)
- ido – (s) Ido language (ISO 639-2 code)
- IDR – (s) Indonesian rupiah (ISO 4217 currency code)
- IDTS – (i) I don't think so
IE
- i.e. – (i) id est (Latin, roughly "that is")
- ie – (s) Interlingue language (ISO 639-1 code)
- IE – (i) Indo-European languages – Internet Explorer – (s) Ireland (ISO 3166 digram) – Iced Earth
- IEA – (i) International Energy Agency
- IEC – (i) International Electrotechnical Commission
- IED – (i) Improvised Explosive Device
- IEEE – (p) Institute of Electrical and Electronics Engineers ("I triple-E")
- IELTS – (a) International English Language Testing System
- IER – (i) Information Exchange Requirement
- IET – (i) Institution of Engineering and Technology
- IET – (ii) Initial Entry Training
- IETF – (i) Internet Engineering Task Force
- IEW – (i) Intelligence and Electronic Warfare
IF
- IFAB – (i) International Football Association Board
- IFAH – (i) International Federation for Animal Health
- IFAP – (i) International Federation of Agricultural Producers, (i) International Fashion Academy Pakistan
- IFC – (i) International Finance Corporation (part of the World Bank) – (a) Independent Film Channel
- IFF – (i) Identification, Friend or Foe – Individually Fresh Frozen – International Flavors and Fragrances
- IFFN – (i) Identification, Friend, Foe, or Neutral
- IFO – (i) Identified Flying Object (see also UFO)
- IFOR – (p) UN Implementation Force – (i) Institute for Operations Research – International Fellowship of Reconciliation
- IFOV – (i) Instantaneous Field of View
- IFPI – (i) International Federation of Phonographic Industries
- IFR – (i) Instrument Flight Rules
- IFRB – (i) International Frequency Registration Board
- IFV – (i) Infantry Fighting Vehicle
IG
- ig – (s) Igbo language (ISO 639-1 code)
- IG –
- (i) Inspector General
- IGFA – International Game Fish Association
- IGM - IATA code for Kingman Airport
- IGNOU – (a) Indira Gandhi National Open University
- IGS – (i) International Ground Station
- IGY – (i) Israeli Gay Youth – International Geophysical Year
IH
- IHÉS – (i) Institut des Hautes Études Scientifiques (French, Institute of Advanced Scientific Studies)
- IHH – (i) Idiopathic Hypogonadotropic Hypogonadism
- IHO – (i/a) International Hydrographic Organization
- IHOP – (i/a) International House of Pancakes, the original name of this American restaurant chain ("EYE-hop")
- IHR – (i) Institute for Historical Review
- IHSI – Institutum Historicum Societatis Iesu (Jesuit Historical Institute)
II
- ii – (s) Sichuan Yi language (ISO 639-1 code)
- II – (s) Two (in Roman numerals)
- IIC or I<sup>2</sup>C - (i) Inter-Integrated Circuit
- IICA – (i) Inter-American Institute for Cooperation on Agriculture
- IIE – (i) Innovative Interstellar Explorer
- iii – (s) Sichuan Yi language (ISO 639-2 code)
- III – (s) Three (in Roman numerals)
- IIMSS – If I May Say So
- IIRC – If I Remember Correctly, If I Recall Correctly
- IISS – (i) International Institute for Strategic Studies
- IIT – (i) Illinois Institute of Technology – Indian Institutes of Technology – Indiana Institute of Technology
- IITM – (i) Image Institute of Technology & Management – Indian Institute of Technology Madras – Indian Institute of Tropical Meteorology
- I/ITSEC – (a) Interservice/Industry Training, Simulation and Education Conference ("eye-it-sec" or "it-sec")
IJ
- IJN – (i) Imperial Japanese Navy (World War II)
- IJWP – (i) Interim Joint Warfare Publication
IK
- ik – (s) Inupiaq language (ISO 639-1 code)
- IKEA – (a) Ingvar Kamprad (the company's founder), Elmtaryd (the farm where he was born and raised), Agunnaryd (a village and parish near the farm)
- iku – (s) (s) Inuktitut language (ISO 639-2 code)
IM
- IM
- (s) Isle of Man (FIPS 10-4 territory code)
- (i) Instant Message (Internet speech)
- IMA
- (i) Intermediate Maintenance Activity
- Institute of Mathematics and Applications
- – (i) International Migratory Bird Day
- IMDb – Internet Movie Database
- IME - (i) In My Experience
- IMF
- (i) id music file/id's music format (audio file format)
- Impossible Missions Force, the protagonist organization in the Mission: Impossible media franchise
- International Monetary Fund (the most common use for the initialism)
- IMHO – (i) In My Humble/Honest Opinion, cf. IMO
- IMIST AMBO – used to facilitate an informed clinical handover between paramedics, emergency department staff or other healthcare similar to SBAR:
