I

For the purposes of this list:

• acronym = an abbreviation pronounced as if it were a word, e.g., SARS = severe acute respiratory syndrome, pronounced to rhyme with cars
• initialism = an abbreviation pronounced wholly or partly using the names of its constituent letters, e.g., CD = compact disc, pronounced cee dee
• pseudo-blend = an abbreviation whose extra or omitted letters mean that it cannot stand as a true acronym, initialism, or portmanteau (a word formed by combining two or more words).

(a) = acronym, e.g.: SARS – (a) severe acute respiratory syndrome
(i) = initialism, e.g.: CD – (i) compact disc
(p) = pseudo-blend, e.g.: UNIFEM – (p) United Nations Development Fund for Women
(s) = symbol (none of the above, representing and pronounced as something else; for example: MHz – megahertz)

Some terms are spoken as either acronym or initialism, e.g., VoIP, pronounced both as voyp and V-O-I-P.

(Main list of acronyms)

• I – (s) Iodine – One (in Roman numerals)

• I2WD or I²WD – (i) U.S. Intelligence and Information Warfare Directorate (CERDEC)

• 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 – (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
  • (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 – (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

• 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

• 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 – (s) Igbo language (ISO 639-1 code)
• IG –
  • (i) Inspector General
  • Instagram
• 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

• 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 – (s) Sichuan Yi language (ISO 639-1 code)
• II – (s) Two (in Roman numerals)
• 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")

• IJN – (i) Imperial Japanese Navy (World War II)
• IJWP – (i) Interim Joint Warfare Publication

• 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
  • (s) Isle of Man (FIPS 10-4 territory code)
  • (i) Instant Message (Internet speech)
• IMA
  • (i) Intermediate Maintenance Activity
  • Institute of Mathematics and Applications
• IMBD – (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: Identification, Method of Injury, Index of concern, Signs, Treatment, Allergies, Medication, Background, and Other
• IML – (i) International Mister Leather
• IMLAST – (i) International Movement for Leisure Activities in Science and Technology – see MILSET
• IMNM - (i) - Immune-mediated necrotizing myopathy a rare, but serious ADR of statins [1]
• IMNSHO – (i) In My Not So Humble Opinion
• IMO (in my opinion) – (i) In My Opinion, also "imo", cf. IMHO
• IMPAC – (a) International Merchant Purchase Authorization Card
• IMPACT – (a) International Medical Products Anti-Counterfeiting Taskforce
• IMPATT – (p) IMPact Avalanche Transit Time diode
• IMPT – (i) Institute of Maxillofacial Prosthetists and Technologists
• IMR – (i) Inzhenernaya Mashina Razgrazhdeniya (Russian Инженерные Машины Разграждения, "Engineer Vehicle Obstacle-Clearing") †
• IMRI
  • (i) Industrial Membrane Research Institute
  • Information Management Research Institute
  • Institut pour le management de la recherche et de l'innovation (French, "Institute for the Management of Research and Innovation")
  • International Market Research Information
  • Intraoperative Magnetic Resonance Imaging
• IMRO
  • Internal Macedonian Revolutionary Organization
  • Irish Music Rights Organisation
• IMRL – (i) Individual Material Readiness List
• IMS
  • (i) Information Management System
  • International Meat Secretariat
  • Ion Mobility Spectrometer
• IMSA
  • (i) Illinois Mathematics and Science Academy
  • International Mind Sports Association
  • International Motor Sports Association
• IMsL – (a) International Ms. Leather
• IMT – (i) Integrated Management Tool
• IMU – (i) International Mathematical Union

• In – (s) Indium
• IN – (s) India (FIPS 10-4 country code; ISO 3166 digram) – Indiana (postal symbol) – Infantry
• ina – (s) Interlingua language (ISO 639-2 code)
• INA – (p) Immigration and Nationality Act
• INAS – (a) International Near-Earth Asteroid Survey
• INC – (i) Indian National Congress, one of the national political parties in India
  • (i) Iglesia ni Cristo (Filipino, "Church of Christ")
  • Indian National Congress
  • International Network of Crackers
  • Iraqi National Congress
• INCITS – (p) InterNational Committee for Information Technology Standards
• ind – (s) Indonesian language (ISO 639-2 code)
• IND – (s) India (ISO 3166 trigram)
• inet – (a) the Internet
• INDIGO – (p) (U.S.) INtelligence DIvision Gaming Operation
• INFORMS – (a) (U.S.) Institute for Operations Research and the Management Sciences
• INFOSEC – (p) Information Security
• INLA – (i) Irish National Liberation Army
• INMARSAT – (p) International Maritime Satellite organization
• INR – (s) Indian rupee (ISO 4217 currency code)
• INRI – (a/i) Iesus Nazarenus Rex Iudæorum (Latin, "Jesus of Nazareth, King of the Jews")
• INRIA – (p) Institut national de recherche en informatique et en automatique
• INS – (i) Immigration and Naturalization Service
• InSAR – (p) Interferometric synthetic aperture radar
• INST – (p) Information Standards and Technology
• in trans. – (p) in transitu (Latin, "in transit")
• INTSUM – (p) Intelligence Summary
• INTERFET – (p) International Force for East Timor

• io – (s) Ido language (ISO 639-1 code)
• IO – (s) British Indian Ocean Territory (ISO 3166 digram; FIPS 10-4 territory code)
• IOC
  • (i) Initial Operational Capability
  • Intergovernmental Oceanic Commission
  • International Olympic Committee
  • International Ornithological Congress
• IOG (formerly IOHK) – Input Output Global. Redirected to Charles Hoskinson
• IOHK – Input Output Hong Kong. Redirected to Charles Hoskinson
• IOLTA – (a) Interest on Lawyer Trust Accounts (charitable funding mechanism, especially for legal aid)
• IOM
  • (i) Iowa, Ohio, Michigan (soybean origin)
  • Institute of Medicine
  • International Organisation for Migration
  • Isle of Man
• IONA – (i) Islands of the North Atlantic (alternate name for Great Britain, Ireland, the Isle of Man, and related islands)
• IoT - (i) Internet of Things
• IOT – (s) British Indian Ocean Territory (ISO 3166 trigram)
• IOT&E – (i) Initial Operational Test and Evaluation
• IOU – (p) "I Owe You" (Promissory note)

• IP –
  • (s) Clipperton Island (FIPS 10-4 territory code)
  • (i) Initial Point – Intellectual Property – Internet Protocol
• IPA – (i) India Pale Ale – International Phonetic Alphabet – Isopropyl alcohol
• IPB – (i) Intelligence Preparation of the Battlefield
• IPCC –
  • (i) Intergovernmental Panel on Climate Change
  • Independent Police Complaints Commission
• ipk – (s) Inupiaq language (ISO 639-2 code)
• IPL – (i) Inferior Parietal Lobule
• IPN – (i) Instytut Pamieci Narodowej (Polish, "Institute for National Memory")
• IPO – (i) Initial public offering
• IPR –
  • (i) In Progress Review
  • Intellectual Property Rights
  • Intelligence Production Requirement
• IPT – (i) Integrated Product/Project Team
• IPTS – (i) Institute for Prospective Technological Studies
• IPTV – (p) Internet Protocol TeleVision
• IPW – (i) Interrogation of Prisoners of War

• iq – (i) idem quod (Latin, "the same as")
• IQ –
  • (i) Intelligence Quotient
  • (s) Iraq (ISO 3166 digram)
• IQD – (s) Iraqi dinar (ISO 4217 currency code)

• Ir – (s) Iridium
• IR
  • (i) Infrared
  • Intelligence requirement (military)
  • (s) Iran (FIPS 10-4 country code; ISO 3166 digram)
  • Iran Air (IATA alpha code) see entry for more
• IRA
  • (i) Individual retirement account
  • (i) Irish Republican Army (any of several armed groups dedicated to Irish republicanism)
  • Internet Research Agency (used in the Mueller report)
• IRAD – (a) Internal Research and Development
• IRAN - (I) Inspect and Repair As Necessary
• IRAS – (p) Infrared Astronomical Satellite
• IRB – (i) International Rugby Board, a former name of World Rugby
• IRBM – (i) Intermediate Range Ballistic Missile
• IRC
  • (i) International Red Cross
  • International reply coupon
  • (i) Internet Relay Chat
• IREA
  • (i) Intermountain Rural Electric Association
  • (i) International Renewable Energy Alliance
  • (p) Iranian Esperanto Association
  • (i) Internet Radio Equality Act
• IRGC - (i) Islamic Revolutionary Guard Corps (branch of Iranian Armed Forces
• IRL
  • (s) Ireland (ISO 3166 trigram)
  • Industrial Research Limited
  • Indy Racing League, former name of the motorsport governing body now known as INDYCAR
  • (i) In real life
• IRM
  • (i) Illinois Railway Museum
  • Inzhenernaya Razvedyvatelnaya Mashina (Russian Инженерная Разведывательная Машина, "Engineer Reconnaissance Vehicle") †
• IRN – (s) Iran (ISO 3166 trigram)
• IRIAF - Islamic Republic of Iran Air Force
• IRINN - Islamic Republic of Iran News Network
• IRO – (i) International Refugee Organisation
• IRQ – (s) Iraq (ISO 3166 trigram)
• IRR – (s) Iranian rial (ISO 4217 currency code)
• IRS – (i) U.S. Internal Revenue Service
• IRSN – (i) Institut de radioprotection et de sûreté nucléaire (French, "Institute for Radiation Protection and Nuclear Safety")
• IRST – (i) Infra-red Search and Track

• is – (s) Icelandic language (ISO 639-1 code)
• IS
  • (s) Iceland (ISO 3166 digram)
  • Israel (FIPS 10-4 country code)
• ISA
  • (i) Individual Savings Account
  • Industry Standard Architecture
  • Instruction Set Architecture
  • International Seabed Authority
• ISAAA – (i) International Service for the Acquisition of Agri-biotech Applications
• ISAF
  • (a) International Sailing Federation
  • International Security Assistance Force
• ISAR – (a) Inverse SAR (Synthetic Aperture Radar)
• ISB – (i) Intermediate Staging Base
• ISBN – (i) International Standard Book Number (ISO 2108)
• ISCCP – (i) International Satellite Cloud Climatology Project
• ISCII – (a) Indian Standard Code for Information Interchange
• ISDN – Integrated Services Digital Network
• ISEF – (a) Intel International Science and Engineering Fair
• ISEN – (i) Internet Search Environment Number
• ISF – (i) Internal Security Force
• ISI
  • Indian Standards Institute, former name of the Bureau of Indian Standards
  • Inter-Services Intelligence (Pakistan)
  • Islamic State of Iraq, an umbrella organization for several Iraqi insurgent groups
• ISIL – (i/a) Islamic State of Iraq and the Levant
• ISIS
  • (i/a) Institute for Science and International Security
  • Islamic State of Iraq and Syria
• ISK – (s) Icelandic krona (ISO 4217 currency code)
• isl – (s) Icelandic language (ISO 639-2 code)
• ISL – (s) Iceland (ISO 3166 trigram)
• ISLN –
  • (i) International Standard Lawyer Number (used initially by LexisNexis Martindale-Hubbell)
  • (i) International School Libraries Network (HQ in Singapore)
  • (s) Isilon Systems, the NASDAQ symbol
• ISM
  • (i) Industrial, scientific or medical
  • (p) Interstellar medium
• ISMB – (i) International Society of Matrix Biologists
• ISMC – (i) Intelligent Sounding Meaningless Conversation
• ISO
  • (i) In Search Of
  • (s) International Organization for Standardization (from the Greek ίσος, isos, meaning "equal")
• ISOGP – (i) Indian Society of Orthodontics for General Practitioners [2]
• ISP
  • (i) International Standardized Profile
  • Internet Service Provider
  • Information Systems Professional
• ISPE – (a/i) International Society for Pharmacoepidemiology
• ISR
  • (i) Intelligence, Surveillance and Reconnaissance
  • (s) Israel (ISO 3166 trigram)
• ISRO – (i) Indian Space Research Organisation
• ISS
  • (i) International Shorebird Survey (North America)
  • International Space Station
• ISSCR – (i) International Society for Stem Cell Research
• ISSN – (i) International standard serial number (ISO 3297)
• IST
  • (i) Information System Technology
  • UCF Institute for Simulation and Training
• ISTAR – (i) Intelligence, Surveillance, Target Acquisition, and Reconnaissance
• ISTC – (i) Institute of Scientific and Technical Communications (UK)
• ISTG – (i) I Swear To God
• ISTS – (i) Intel Science Talent Search
• ISU
  • (i) Integrated Sight Unit
  • International Skating Union

• it – (s) Italian language (ISO 639-1 code)
• IT
  • (i) InferoTemporal (neurophysiology)
  • Information Technology
  • (s) Italy (FIPS 10-4 country code; ISO 3166 digram)
• ita – (s) Italian language (ISO 639-2 code)
• ITA – (s) Italy (ISO 3166 trigram)
• ITAG – (i) Inertial Terrain-Aided Guidance
• ITALY – (a) I'll Truly Always Love You
• ITAS – (i) Improved Target Acquisition Sight
• ITC
  • (i) Incorporated Television Company (defunct British television production company)
  • InferoTemporal Cortex (neurophysiology)
• ITCZ – (i/p) Intertropical Convergence Zone
• ITEC – (a) Information Technology Exposition & Conference
• ITEMS – (a) Interactive Tactical Environment Management System
• ITER – (a) International Thermonuclear Experimental Reactor
• ITF – (a) International Tennis Federation
• ITK – (a) In The Know
• ITN – (i) Independent Television News (British)
• ITS
  • (i) Incompatible Time-sharing System
  • Individual Training Standards
• ITT – (i) International Telephone and Telegraph (U.S.)
• ITTO – (i) International Tropical Timber Organization
• ITU
  • (i) Intent-to-Use
  • International Telecommunication Union (International Telegraph Union 1865–1932)

• iu – (s) (s) Inuktitut language (ISO 639-1 code)
• IUCN – (i) International Union for the Conservation of Nature and Natural Resources (World Conservation Union)
• IUD – (i) Intrauterine device (https://www.plannedparenthood.org/learn/birth-control/iud)
• IUI
  • (i) Indiana University Indianapolis, to be established in 2024 upon the dissolution of Indiana University–Purdue University Indianapolis (IUPUI, below)
  • Intrauterine insemination (http://americanpregnancy.org/infertility/intrauterine-insemination/)
• IUPAC – (a) International Union of Pure and Applied Chemistry (pronounced "eye-yoo-pac")
• IUPUI – (a) Indiana University–Purdue University Indianapolis
• IUSS
  • (i) Integrated Undersea Surveillance System
  • Integrated Unit Simulation System
  • International Union of Soil Sciences

• IV – (s) Côte d'Ivoire (FIPS 10-4 country code; from Ivory Coast) – Four (in Roman numerals) – (i) IntraVenous (as in intravenous drip or intravenous therapy)
• IVD – (i) Internet Video Device, intra vas device
• Iveco – (p) Industrial Vehicles Corporation
• IVF – (i) In Vitro Fertilisation
• IVI – (i) Interchangeable Virtual Instrument
• IVIS – (i/a) Inter-Vehicle Information System
• IVL – (i) Inter-Visibility Line
• IVM – (i) In Vitro [Oocyte] Maturation
• IVO – (i) In Vicinity Of

• IW – (i) Impact Wrestling
• IW – (i) Information Warfare
• IWARS – (p) Infantry Warrior Simulation
• IWC – (i) International Whaling Commission
• IWT – (i) Illegal Wildlife Trade
• IWW – (i) Industrial Workers of the World

• IX – (s) Nine (in Roman numerals)
• IXT – (s) IntraText digital library; IntraText lexical hypertext

• IY – (s) Saudi–Iraqi neutral zone (FIPS 10-4 territory code; obsolete 1993)
• Iykyk (acronym) – (i) If You Know You Know

• IZ – (s) Iraq (FIPS 10-4 country code)