

| Acronym | Sense | Language | Topics | 
|---|---|---|---|
| UDC | Universele Decimale Classificatie = UDK | Universala Dekuma Klasifiko | In Esperanto = UDC | Universal Decimal Classification | In English = CDU | Classification Décimale Universelle | In French = CDU | Clasificación Decimal Universal | In Spanish = UDC | Universel Decimal Classifikation | In Danish | In Dutch | → Libraries | 
| UDC | Universel Decimal Classifikation = UDK, CDU (look above) | In Danish | → Libraries | 
| UDC | Utility Distribution Center | In English | |
| UDC | Unione dei Democratici Cristiani e di Centro | In Italian | → 32916 | 
| UDDI | Universal Description Discovery and Integration | In English | → Networks, communication → Telecommunications | 
| UDECAM | Union des Entreprises de Conseil et Achat Média | In French | → Organizations and associations → 659 | 
| UDF | Union pour la Démocratie Française | In French | → Political parties and movements → France | 
| UDF | Unit Development Folder | In English | |
| UDHR | Universala Deklaracio de Homaj Rajtoj = DUDH | Déclaration Universelle des Droits de l'Homme | In French = UDHR | Universal Declaration of Human Rights | In English = DUDH | Declaración Universal de los Derechos Humanos | In Spanish = GEAU | Giza Eskubideen Aldarrikapen Unibertsala | In Basque = VDLP | Všeobecná deklarace lidských práv | In Czech = UVMR | Universele Verklaring van Menseregte | In Afrikaans = DUDH | Declaración Universal dos Dereitos Humanos | In Galician = MSÞ | Mannréttindayfirlýsing Sameinuðu þjóðanna | In Icelandic = DUDU | Dichiarazione Universale dei Diritti Umani | In Italian = PDPC | Powszechna Deklaracja Praw Człowieka | In Polish = DUDH | Declaração Universal dos Direitos Humanos | In Portuguese = DUDO | Declaraţia Universală a Drepturilor Omului | In Romanian = ВДПЧ | Всеобщая декларация прав человека | In Russian = İHEB | İnsan Hakları Evrensel Bildirisi | In Turkish | In Esperanto | → Human rights | 
| UDHR | Universal Declaration of Human Rights = DUDH, GEAU, VDLP, UVMR, MSÞ, DUDU, PDPC, DUDO, ВДПЧ, İHEB (look above) | In English | → Human rights | 
| UDI | Uitspanning Door Inspanning | In Dutch | → Organizations and associations → Sport, physical exercises | 
| UDIC | Union française des Distributeurs, Grossistes et Importateurs en Chaussures | In French | → Organizations and associations → Trade → Leather industry → France | 
| UDIROS | Us Doarp Is Rijk Oan Sport | In Dutch | → Organizations and associations → Sport, physical exercises | 
| UDIS | Unidad Docente de Ingeniería del Software | In Spanish | → Software | 
| UDK | Universala Dekuma Klasifiko = UDC, CDU (look above) | In Esperanto | → Libraries | 
| ÜDM | Üst Düzey Mimari | In Turkish | |
| UdM | Université des Montagnes (www.udesmontagnes.org) | In French | → Higher education, universities | 
| UDMH | Unsymmetrical Dimethylhydrazine | In English | → Chemical technology | 
| UDMH/H | Unsymmetrical Dimethylhydrazine Hydrazine Blend | In English | → Chemical technology | 
| UDO | Ultra Density Optical | In English | |
| UDO | Uithoudingsvermogen Door Oefening | In Dutch | → Organizations and associations → Sport, physical exercises | 
| UDOP | Ultrahigh Doppler | In English | |
| UDP | User Datagram Protocol | In English | → Networks, communication | 
| UDP/IP | User datagram protocol/Internet Protocol | In English | → Internet | 
| UdPPC | Union des Professeurs de Physique et de Chimie | In French | → Education → Physics → Chemistry | 
| UDR | Union pour la Défense de la République | In French | → Political parties and movements | 
| UDR | Union des Démocrates pour la République | In French | → Political parties and movements | 
| UDS | Universal Documentation System | In English | → Documentation → Knowledge management | 
| UDS | Utility Distribution System | In English | |
| UDS | Uniform Data Systems | In English | → Data | 
| ÜDS | Üniversiteler Arası Yabancı Dil Sınavı | In Turkish | → Higher education, universities → Linguistics | 
| UDSF | United Democratic Sudan Forum | In English | → Political parties and movements | 
| UDSP | Union Départementale des Sapeurs-Pompiers | In French | → Organizations and associations → Firefighting | 
| UDSR | Union Démocratique et Socialiste de la Résistance | In French | → Socialist parties → History | 
| UdSSR | Union der Sozialistischen Sowjetrepubliken = URSS | Unaniezh ar Republikoù Sokialour Soviedel | In Breton = URSS | Union des Républiques Socialistes Soviétiques | In French = USSR | Unie van Sosialistiese Sowjetrepublieke | In Afrikaans = USSR | Union of Soviet Socialist Republics | In English = СССР | Сою́з Сове́тских Социалисти́ческих Респу́блик | In Russian = CCCP | Съюзът на съветските социалистически републики | In Bulgarian = SSSR | Soyuz Sovetskikh Sotsialisticheskikh Respublik | In Russian = URSS | Unión de Republicas Sozialistas Sobieticas | In Aragonese = XRSS | Xunión de les Repúbliques Socialistes Soviétiques | In Asturian = SSRİ | Sovet Sosialist Respublikaları İttifaqı | In Azerbaijani = TSRS | Tarybu Socialistiniu Respubliku Sajunga | In Baltic languages = SSSR | Savez Sovjetskih Socijalističkih Republika | In Serbo-Croatian = URSS | Unió de Repúbliques Socialistes Soviètiques | In Catalan = SSSR | Svaz sovětských socialistických republik | In Czech = USSR | Unio de Sovetaj Socialismaj Respublikoj | In Esperanto = CCCP | Социаллă Совет Республикисен Союзĕ | In Chuvash = USSR | Unionen af Socialistiske Sovjetrepublikker | In Danish = URSS | Unione delle Repubbliche Socialiste Sovietiche | In Italian = ZSRR | Związek Socjalistycznych Republik Radzieckich | In Polish = SSKS | Szovjet Szocialista Köztársaságok Szövetsége | In Hungarian = ΕΣΣΔ | Ένωση Σοβιετικών Σοσιαλιστικών Δημοκρατιών | In Greek = URSS | Unión de Repúblicas Socialistas Soviéticas | In Spanish = NSVL | Nõukogude Sotsialistlike Vabariikide Liit | In Estonian = SESB | Sobietar Errepublika Sozialisten Batasuna | In Basque = USSR | Uny fan Sosjalistyske Sowjetrepublyken | In Frisian = ԽՍՀՄ | Խորհրդային Սոցիալիստական Հանրապետությունների Միություն | In Armenian = URSS | Unión das Repúblicas Socialistas Soviéticas | In Galician = სსრკ | საბჭოთა სოციალისტური რესპუბლიკების კავშირი | In Georgian = URSS | Unio Rerum Publicarum Socialisticarum Sovieticarum | In Latin = CCPC | Советтик Социалисттик Республикалар Союзу | In Kirghiz = UdSSR | Unioun vun de Sozialistesche Sowjetrepubliken | In Letzeburgesh = PSRS | Padomju Sociālistisko Republiku Savienība | In Latvian = СССР | Сојуз на Советските Социјалистички Републики | In Macedonian = УРСС | Униуня Републичилор советиче Сочиалисте | In Moldavan = KRSS | Kesatuan Republik Sosialis Soviet | In Malay = USSR | Unie van Socialistische Sovjetrepublieken | In Dutch = SSSR | Sambandet av Sosialistiske Sovjet-Republikkar | In Nynorsk = SSSR | Samveldet av sovjetiske sosialistrepublikker | In Norwegian = URSS | Unnion d'Républyiques Socialistes Soviétiques | In Norman = URSS | União das Repúblicas Socialistas Soviéticas | In Portuguese = URSS | Union de las Republicas Socialistas Sovieticas | In Occitan = SSRH | Susyalista Suwit Republikakunap Huñun | In Quechua = ССРЦ | Советон Социалистон Республикæты Цæдис | In Ossetian = URSS | Uniunea Republicilor Sovietice Socialiste | In Romanian = URSS | Unioni dî ripùbblichi sucialisti suviètichi | In Sicilian = ZSSR | Zveza sovjetskih socialističnih republik | In Slovenian = СССР | Савез Совјетских Социјалистичких Република | In Serbian = SSCB | Sovyet Sosyalist Cumhuriyetler Birliği | In Turkish = СРСР | Союз Радянських Соціалістичних Республік | In Ukrainian = SSRB | Sovet Sosialistik Republiklar Berlege | In Tatar = SSRI | Sovet Sotsialistik Respublikalar Ittifoqi | In Uzbek | In German | → International relations → Geography | 
| UdSSR | Unioun vun de Sozialistesche Sowjetrepubliken = URSS, USSR, СССР, CCCP, SSSR, XRSS, SSRİ, TSRS, ZSRR, SSKS, ΕΣΣΔ, NSVL, SESB, ԽՍՀՄ, სსრკ, CCPC, PSRS, УРСС, KRSS, SSRH, ССРЦ, ZSSR, SSCB, СРСР, SSRB, SSRI (look above) | In Letzeburgesh | → International relations → Geography | 
| UDT | Union Démocratique du Travail | In French | → Political parties and movements | 
| UDTA | Ugandan Development Theater Association | In English | → Associations → Theatre | 
| UDWDM | Ultra Dense Wavelength Division Multiplexing | In English | → Networks, communication → Telecommunications | 
| UE | Union Européenne (http://europa.eu) = EU | European Union | In English = UE | Unió Europea | In Catalan = UE | Unaniezh Europa | In Breton = EU | Europäische Union | In German = UE | Unia Europejska | In Polish = EU | Europese Unie | In Afrikaans = UE | Unión Europeya | In Aragonese = EU | Evropská Unie | In Czech = ЕС | Европейският съюз | In Bulgarian = EU | Eùropejskô Ùnijô | In Kashubian = ΕΕ | Ευρωπαϊκή Ένωση | In Greek = EU | Europæiske Union | In Danish = UE | Undeb Ewropeaidd | In Welsh = EU | Eŭropa Unio | In Esperanto = JU | Jeropeeske Uny | In Frisian = AE | An tAontas Eorpach | In Irish = EB | Europar Batasuna | In Basque = EU | Europska Unija | In Croatian = UE | Unión Europea | In Spanish = EU | Euroopan unioni | In Finnish = EU | Evropska Unija | In Bosnian = UÛ | Unnion Ûropéenne | In Norman = ES | Europas Sājonga | In Baltic languages = UE | Uniaun Europeia | In Tetum = UE | Unyong Europeo | In Tagalog = EU | Európai Unió | In Hungarian = EU | Europeiska unionen | In Swedish = EU | Europana Uniono | In Ido = UE | Uni Eropa | In Indonesian = ESB | Evrópusambandið | In Icelandic | In French | → International relations → European Union → Europe | 
| UE | Unió Europea (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Catalan | → International relations → European Union → Europe | 
| UE | Unaniezh Europa (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Breton | → International relations → European Union → Europe | 
| UE | Unia Europejska (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Polish | → International relations → European Union → Europe | 
| UE | Unión Europeya (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Aragonese | → International relations → European Union → Europe | 
| UE | Undeb Ewropeaidd (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Welsh | → International relations → European Union → Europe | 
| UE | Unión Europea (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Spanish | → International relations → European Union → Europe | 
| UE | Unité d'Enseignement | In French | → Education | 
| UE | Uniaun Europeia (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Tetum | → International relations → European Union → Europe | 
| UE | Unyong Europeo (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Tagalog | → International relations → European Union → Europe | 
| UE | User Equipment | In English | |
| UE | Uni Eropa (http://europa.eu) = EU, ЕС, ΕΕ, JU, AE, EB, UÛ, ES, ESB (look above) | In Indonesian | → International relations → European Union → Europe | 
| UEA | Universala Esperanto Asocio (www.uea.org) | In Esperanto | → Associations → Artificial languages (linguistics) | 
| UEA | University of East Anglia (www.uea.ac.uk) | In English | → Higher education, universities → United Kingdom | 
| UEA | Utah Education Association | In English | → Associations → Education → United States | 
| UEA | United Energy Associates (www.uea.com) | In English | → Energy economics → Electrical engineering → Environmental technology, water supply, waste management | 
| UEA | Urban Exploration Alberta | In English | → Civil engineering → Canada | 
| UEA | Universidade do Estado do Amazonas | In Portuguese | → Higher education, universities | 
| UEAF | Union des Étudiants Algériens de France | In French | → Organizations and associations → Higher education, universities → France | 
| UEAPME | Union Européenne de l'Artisanat et des Petites et Moyennes Entreprises (www.ueapme.com) | In French | → Organizations and associations | 
| UEAPME | Union Européenne de l'Artisanat et des Petites et Moyennes Entreprises | In French | → Organizations and associations → 3384 → Europe | 
| UEAtc | Union Européenne pour l'Agrément technique dans la construction | In French | → Organizations and associations → Construction | 
| UEC | Union Européenne de Cyclisme | In French | → Organizations and associations → Sport, physical exercises | 
| UEC | Union des Étudiants Communistes | In French | → Communist parties → Higher education, universities | 
| UECBu | University Electro-Communications Bulletin | In English | → Serial publications, periodicals → Telecommunications | 
| UEF | Unité équivalent fibrinogène | In French | → Physiology | 
| UEF | Unio de la Europaj Federistoj = UEF | Union of European Federalists | In English | In Esperanto | → Political parties and movements | 
| UEF | Union of European Federalists = (look above) | In English | → Political parties and movements | 
| UEF | Unité d'Enseignement et de Recherche | In French | → Research policy → Education | 
| UEFA | Uny fan Europeeske Fuotbal Assosjaasjes | In Frisian | → Organizations and associations → Sport, physical exercises | 
| UEFA | Union Européenne de Football Association (www.uefa.com) = UEFA | Union of European Football Associations | In English | In French | → Organizations and associations → Football and rugby | 
| UEFA | Union of European Football Associations (www.uefa.com) = (look above) | In English | → Organizations and associations → Football and rugby | 
| UEL | Urala Esperanto-Ligo | In Esperanto | → Organizations and associations → Artificial languages (linguistics) | 
| UEM | Unión Económica y Monetaria = EMU | Economische Monetaire Unie | In Vlaams = EMU | Economic and Monetary Union | In English = EMU | Ekonomiska och monetära unionen | In Swedish = UGiW | Unia Gospodarcza i Walutowa | In Polish = EMU | Economische en Monetaire Unie | In Dutch = EWG | Europäesch Wirtschafts- a Währungsunioun | In Letzeburgesh = EGMU | Európai Gazdasági és Monetáris Unió | In Hungarian = UEM | Union économique et monétaire | In French = EWWU | Europäische Wirtschafts- und Währungsunion | In German = ØMU | Økonomiske og Monetære Union | In Danish = EMU | Evropská měnová unie | In Czech = UEM | Unione Economica e Monetaria | In Italian = UEM | Unió econòmica i monetària | In Catalan | In Spanish | → Economics → European Union | 
| UEM | Union Européenne Motocyclisme | In French | → Organizations and associations → Transport and postal services | 
| UEM | Union En Mouvement | In French | → Political parties and movements | 
| UEM | Union économique et monétaire = EMU, UGiW, EWG, EGMU, EWWU, ØMU (look above) | In French | → Economics → European Union | 
| UEM | Unione Economica e Monetaria = EMU, UGiW, EWG, EGMU, EWWU, ØMU (look above) | In Italian | → Economics → European Union | 
| UEM | Unió econòmica i monetària = EMU, UGiW, EWG, EGMU, EWWU, ØMU (look above) | In Catalan | → Economics → European Union | 
| UEMOA | Union Économique et Monétaire Ouest-Africaine = UEMOA | Unió Econòmica i Monetària de l'Oest d'Àfrica | In Catalan | In French | → International economic cooperation → Africa | 
| UEMOA | Unió Econòmica i Monetària de l'Oest d'Àfrica = (look above) | In Catalan | → International economic cooperation → Africa | 
| UEN | Union pour l'Europe des nations (www.uengroup.org) = UEN | Union für ein Europa der Nationen | In German = UEN | Unio por Eŭropo de Nacioj | In Esperanto = UEN | Unión por la Europa de las Naciones | In Spanish = UEN | Unión pola Europa das Nacións | In Galician = UEN | Unione per l'Europa delle Nazioni | In Italian = UEN | Unie voor een Europa van Nationale Staten | In Dutch = UEN | Unia na rzecz Europy Narodów | In Polish = UEN | União para a Europa das Nações | In Portuguese = UNE | Unionen för nationernas Europa | In Swedish = UEN | Union for Europe of the Nations | In English | In French | → Political parties and movements → European Union | 
| UEN | Union für ein Europa der Nationen (www.uengroup.org) = UNE (look above) | In German | → Political parties and movements → European Union | 
| UEN | Unio por Eŭropo de Nacioj (www.uengroup.org) = UNE (look above) | In Esperanto | → Political parties and movements → European Union | 
| UEN | Unión por la Europa de las Naciones (www.uengroup.org) = UNE (look above) | In Spanish | → Political parties and movements → European Union | 
| UEN | Unión pola Europa das Nacións (www.uengroup.org) = UNE (look above) | In Galician | → Political parties and movements → European Union | 
| UEN | Unione per l'Europa delle Nazioni (www.uengroup.org) = UNE (look above) | In Italian | → Political parties and movements → European Union | 
| UEN | Unie voor een Europa van Nationale Staten (www.uengroup.org) = UNE (look above) | In Dutch | → Political parties and movements → European Union | 
| UEN | Unia na rzecz Europy Narodów (www.uengroup.org) = UNE (look above) | In Polish | → Political parties and movements → European Union | 
| UEN | União para a Europa das Nações (www.uengroup.org) = UNE (look above) | In Portuguese | → Political parties and movements → European Union | 
| UEN | Union for Europe of the Nations (www.uengroup.org) = UNE (look above) | In English | → Political parties and movements → European Union | 
| UEO | Union de l'Europe Occidentale = WEU | Western European Union | In English = WEU | Westeuropäische Union | In German | In French | → International relations | 
| UEP | Undergraduate Exchange Program | In English | → Education | 
| UEP | Unité d'Experience Professionnelle | In French | → Labour, labour economics | 
| UEP | Union des Étudiants pour le Progrès | In French | → Political parties and movements | 
| UEPG | Union Européenne des Producteurs de Granulats (www.uepg.eu) | In French | → Organizations and associations → Civil engineering → Construction → Europe | 
| UER | Unique-Equipment Register | In English | |
| UER | Union Européenne de Radio-télévision (www.ebu.ch) = EBU | European Broadcasting Union | In English = ЕСРТ | Европейски съюз за радио и телевизия | In Bulgarian = ЄТС | Європейський Телерадіомовний Союз | In Ukrainian = ЕВС | Европейский вещательный союз | In Russian = UER | União Europeia de Radiodifusão | In Portuguese | In French | → Organizations and associations → Telecommunications | 
| UER | União Europeia de Radiodifusão (www.ebu.ch) = EBU, ЕСРТ, ЄТС, ЕВС (look above) | In Portuguese | → Organizations and associations → Telecommunications | 
| UER | Unité d'Enseignement et de Recherche | In French | → Education → Research policy | 
| UES | Urala Esperanto-Societo | In Esperanto | → Organizations and associations → Artificial languages (linguistics) | 
| UES | Unified Energy System = ЕЭС | Единые Энергетические Системы | In Russian | In English | → Energy economics → Electrical engineering | 
| UESL | Union d'Économie Sociale pour le Logement (www.uesl.fr) | In French | → Organizations and associations → Economics → Accommodation | 
| UETP | University Enterprise Training Partnership | In English | → Higher education, universities → Labour, labour economics | 
| UF | Union des Fabricants | In French | → Organizations and associations → Industrial property | 
| UFA | Union Fédérale Anarchiste | In French | → Organizations and associations → Anarchist organizations | 
| UFA | Unité de Formation par Apprentissage | In French | → Education → Labour, labour economics | 
| UFAR | Union Française des Anciens du Rugby | In French | → Organizations and associations → Football and rugby → France | 
| UFARCO | Union Française des Associations Régionales de Consultants | In French | → Organizations and associations → Consulting → France | 
| UFAS | Uniform Federal Accessibility Standards | In English | → Standardization | 
| UFAW | Universities Federation for Animal Welfare (www.ufaw.org.uk) | In English | → Organizations and associations → Higher education, universities → Veterinary medicine → United Kingdom | 
| UFC | Udviklings- og formidlingscenter for socialt arbejde | In Danish | |
| UFC | Utrechtsche Football Club | In Dutch | → Organizations and associations → Football and rugby → Netherlands | 
| UFCC | Union Française du Commerce Chimique | In French | → Organizations and associations → Trade → Food technology → France | 
| UFD | User File Directory | In English | → Software → Files | 
| UFE | Unuiĝo Franca por Esperanto (http://esperanto-france.org) = UFE | Union Française pour l'Espéranto | In French | In Esperanto | → Organizations and associations → Artificial languages (linguistics) → France | 
| UFE | Union Française pour l'Espéranto (http://esperanto-france.org) = (look above) | In French | → Organizations and associations → Artificial languages (linguistics) → France | 
| UFE | Uterine Fibroid Embolisation | In English | → Medicine | 
| UFE | Union Française de l'Électricité | In French | → Organizations and associations → Electrical engineering → France | 
| UFF | Union des Femmes Françaises | In French | → Political parties and movements → History → France | 
| UFF | Union Financière de France | In French | → Banks | 
| UFFEJ | Union Française du Film pour l'Enfance et la Jeunesse (www.uffej.net) | In French | → Organizations and associations → Cinema, movies → Education → France | 
| UFM | Union Française des Maréchaux-ferrants | In French | → Organizations and associations → Applied sciences, technology → France | 
| UFM | Universidad Francisco Marroquín | In Spanish | → Higher education, universities | 
| UFM | Utilisateurs Francophones de Medidoc/Clinidoc | In French | → Organizations and associations → Computer science → Medicine | 
| UFO | Unidentifiziertes Flugobjekt = OVNI | Objet Volant Non Identifié | In French = OVNI | Objecte Volador No Identificat | In Catalan = НЛО | Неидентифициран летящ обект | In Bulgarian = OVNI | Objeto Volador No Identificado | In Spanish = UFO | Unidentified Flying Object | In English = UFO | Unknown Flying Object | In English = UFO | Uidentificeret flyvende objekt | In Danish = NIFO | Neidentigita Fluganta Objekto | In Esperanto = UFO | Unbekend fleanend objekt | In Frisian = עב"מ | עצם בלתי מזוהה | In Hebrew = OVNI | Oggetto Volante Non Identificato | In Italian = NLO | Neidentificēts lidojošs objekts | In Latvian = UFO | Uidentifisert flygende objekt | In Norwegian = UFO | Uidentifisert flygande objekt | In Nynorsk = NOL | Niezidentyfikowany Obiekt Latający | In Polish = OVNI | Objeto Voador Não Identificado | In Portuguese = OZN | Obiect Zburător Neidentificat | In Romanian = НЛО | Неопознанный летающий объект | In Russian = NLO | Neidentifikovani leteći objekat | In Serbo-Croatian | In German | → Astronautics | 
| UFO | Unidentified Flying Object = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In English | → Astronautics | 
| UFO | Unknown Flying Object = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In English | → Astronautics | 
| UFO | Uidentificeret flyvende objekt = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In Danish | → Astronautics | 
| UFO | Unbekend fleanend objekt = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In Frisian | → Astronautics | 
| UFO | Uidentifisert flygende objekt = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In Norwegian | → Astronautics | 
| UFO | Uidentifisert flygande objekt = OVNI, НЛО, NIFO, עב"מ, NLO, NOL, OZN (look above) | In Nynorsk | → Astronautics | 
| UFOLEP | Union Française des Oeuvres Laïques d'Éducation Physique (www.ufolep.org) | In French | → Organizations and associations → Sport, physical exercises | 
| UFON | Unie van Filiaal- en Franchise Optiekbedrijven Nederland | In Dutch | → Organizations and associations → Netherlands | 
| UFOP | Universidade Federal de Ouro Preto (www.ufop.br) | In Portuguese | → Higher education, universities → Brazil | 
| UFP | Union des Forces de Progrès | In French | → Political parties and movements | 
| UFP | Usinage et Formage des Plastiques | In French | → Plastic industry | 
| UFP | United Federation of Planets | In English | → Organizations and associations → Politics → Literature | 
| UFP | Union des Forces Progressistes | In French | → Political parties and movements | 
| UFP | Universidade Fernando Pessoa | In Portuguese | → Higher education, universities | 
| UFP | Unión Federal de Policia | In Spanish | → Organizations and associations → Police | 
| UFR | Unité de Formation et de Recherche | In French | → Education → Research policy | 
| UFRGS | Universidade Federal do Rio Grande do Sul | In Portuguese | → Higher education, universities | 
| UGAC | Union des Groupes Anarchistes Communistes | In French | → Organizations and associations → Anarchist organizations → Communist parties | 
| UGAL | Union des Groupes Autonomes Libertaires | In French | → Organizations and associations → Anarchist organizations | 
| UGB | Unité Gros Bétail | In French | → Agricultural sciences | 
| UGC | University Grants Committee | In English | → Higher education, universities | 
| UGC | User Generated Content | In English | → Networks, communication → Computer-based techniques | 
| UGC | Nova Acta Regiae Societatis Scientiarum Upsaliensis | In Latin | → Serial publications, periodicals → Mathematics and natural sciences | 
| UGC | Union Géophysique Canadienne (www.cgu-ugc.ca) = CGU | Canadian Geophysical Union | In English | In French | → Organizations and associations → Geophysics → Canada | 
| UGFR | Union Gaulliste pour une France Républicaine | In French | → Political parties and movements → France | 
| UGGI | Union Géodésique et Géophysique Internationale (www.iugg.org) = IUGG | International Union of Geodesy and Geophysics | In English | In French | → Organizations and associations → Geodesy, cartography → Geophysics | 
| UGIF | Union Générale des Israélites de France | In French | → Organizations and associations → Political parties and movements → Judaism → France | 
| UGiW | Unia Gospodarcza i Walutowa = UEM, EMU, EWG, EGMU, EWWU, ØMU (look above) | In Polish | → Economics → European Union | 
| UGL | Undergraduate Library | In English | → Libraries → Education | 
| UGR | Universidad de Granada (www.ugr.es) | In Spanish | → Higher education, universities → Spain | 
| UGSJR | US Geological Survey Journal Research | In English | → Serial publications, periodicals → Earth sciences → United States | 
| UGT | Unión General de Trabajadores | In Spanish | → Organizations and associations → Labour, labour economics | 
| UGT | União Geral de Trabalhadores | In Portuguese | → Organizations and associations → Labour, labour economics | 
| UHA | Ukrainian Historical Association | In English | → Associations → History | 
| UHA | Urban History Association | In English | → Associations → 93031 | 
| UHC | Uni Hernani Combinatie | In Dutch | → Organizations and associations → Sport, physical exercises | 
| UHCCI | Union of Hellenic Chambers of Commerce and Industry | In English | → Organizations and associations → Trade → Industry, industrial policy → Greece | 
| UHCW | Unquy hark'aypa chaskisqa waqlliynin = AIDS | Acquired Immune Deficiency Syndrome | In English = SIDA | Syndrome d'Immuno-Déficience Acquise | In French = VIGS | Verworwe Immuniteitsgebreksindroom | In Afrikaans = SIDA | Síndrome de Inmuno-Deficiencia Adquirida | In Occitan = SIDA | Sindromo di Imuno-Defekteso Aquirita | In Ido = AIDS | Akirita Imuno-Deficita Simptomaro | In Esperanto = SIDA | Sindrome d'inmunodefizienzia aquirita | In Aragonese = СПИН | Синдром на придобитата имунна недостатъчност | In Bulgarian = QİÇS | Qazanılmış İmmun Çatışmazlığı Sindromu | In Azerbaijani = SIDA | Síndrome d'Immunodeficiència Adquirida | In Catalan = HIES | Hartutako Immuno Eskasiaren Sindromea | In Basque = SIDA | Síndrome de Inmunodeficiencia Adquirida | In Spanish = SEIF | Siondróm Easpa Imdhíonachta Faighte | In Irish = AIDS | Annlochd Inneamh Dìon-Slàinte | In Scottish Gaelic = ՁԻԱՀ | Ձեռքբերովի Իմունային Անբավարվածության Համախտանիշ | In Armenian = SCDI | Syndromis Comparatis Defectu Immunitatis | In Latin = 에이즈 | 후천성 면역 결핍 증후군 | In Korean = შიდსი | შეძენილი იმუნური დეფიციტის სინდრომი | In Georgian = СИДА | Синдромот на стекнат имунолошки дефицит | In Macedonian = СИДА | синдром стеченог имунолошког дефицита | In Serbian = AIDS | Akvirírani imúnski deficítni sindróm | In Slovenian = СПИД | Синдром приобретённого иммунного дефицита | In Russian = SIDA | Sindromul Imunodeficienţei Autodobândite | In Romanian = SIDA | Síndrome da imunodeficiência adquirida | In Portuguese = AIDS | Hội chứng Suy giảm Miễn dịch Mắc phải | In Vietnamese = СНІД | Cиндром набутого імунодефіциту | In Ukrainian = AIDS | Alınğan İmmun Defisit Síndromı | In Tatar = UKIMWI | Upungufu wa Kinga Mwilini | In Swahili | In Quechua | → Immunology and allergy → Infectious diseases | 
| UHF | Ultrahigh Frequency | In English | |
| UHF | Ultra High Frequency = УКВ | Ультракороткие волны | In Russian = UKW | Ultrakurzwelle | In German | In English | → Telecommunications | 
| UHF/VHF | Ultra High Frequency/Very High Frequency | In English | → Telecommunications | 
| UHP | Université Henri Poincaré (www.uhp-nancy.fr) | In French | → Higher education, universities → France | 
| UHSV | Utrechtse Handelsreizigers Sport Vereniging | In Dutch | → Organizations and associations → Sport, physical exercises → Netherlands | 
| UHT | Umbilical Handling Technician | In English | |
| UHT | Ukrayins'ke Heral'dychne Tovarystvo | In Ukrainian | → Organizations and associations → Flags, banners | 
| UHT | Українсьҝе ґералъдичне товариство | In Ukrainian | → Organizations and associations → Flags, banners | 
| UI | User Interface | In English | → Human-computer interaction | 
| UIA | Uganda Investment Authority | In English | → 33972 | 
| UIA | Union Internationale des Architectes (www.uia-architectes.org) | In French | → Organizations and associations → Architecture | 
| UIC | University of Illinois at Chicago (www.uic.edu) | In English | → Higher education, universities → United States | 
| UIC | Union Internationale des Chemins de fer | In French | → Transport and postal services | 
| UIC | Universal Instruments Corporation | In English | → Engineering, technology | 
| UIC | Union des Industries Chimiques (www.uic.fr) | In French | → Organizations and associations → Chemical technology → France | 
| UIC | Unione Italiana Casting (www.unioneitalianacasting.it) | In Italian | → Organizations and associations → Cinema, movies → Italia | 
| UIC | Unit Identification Code | In English | |
| UICB | International Union of Building Centres (www.uicb.org) | In English | → Organizations and associations → Construction | 
| UICC | Universal Integrated Circuit Card | In English | → Electronics | 
| UICC | Unione Italiana Circoli del Cinema (www.uicc.it) | In Italian | → Organizations and associations → Cinema, movies → Italia | 
| UICN | Union Internationale pour la Conservation de la Nature | In French | → Organizations and associations → Environmental protection | 
| UIDH | Union Interafricaine des Droits de l'Homme (www.iuhr.org) = IUHR | Inter-African Union of Human Rights | In English | In French | → International relations → Human rights → Fundamental rights → Africa | 
| UIEA | Universala Islama Esperanto-Asocio | In Esperanto | → Associations → Islam → Artificial languages (linguistics) | 
| UIIP | User Integration Implementation Plan | In English | |
| UIISC | Unité d'Instruction et d'Intervention de la Sécurité Civile | In French | → Public administration, government | 
| UIL | Unione Italiana del Lavoro (www.uil.it) | In Italian | → Organizations and associations → Labour, labour economics → Italia | 
| UIMA | Unstructured Information Management Architecture | In English | → Software | 
| UIML | User Interface Markup Language | In English | → Programming languages → Human-computer interaction | 
| UIMM | Union des Industries et Métiers de la Métallurgie (www.uimm.fr) | In French | → Organizations and associations → Metallurgy → France | 
| UIMS | User Interface Management System | In English | → Human-computer interaction | 
| UIOM | Usine d'Incinération des Ordures Ménagères | In French | → Environmental technology, water supply, waste management | 
| UIR | Universal Infrared Receiver | In English | → Computer hardware → Peripheral devices | 
| UIR | Union Interprofessionnelle de la Réunion | In French | → Organizations and associations → Labour, labour economics | 
| UIR | Unité d'Intervention de Réserve | In French | → Military affairs | 
| UIRF | University of Iowa Research Foundation (http://research.uiowa.edu/techtransfer/) | In English | → Foundations → Higher education, universities → United States | 
| UiS | Universitetet i Stavanger (www.uis.no) | In Norwegian | → Higher education, universities → Norway | 
| UIT | Ultraviolet Imaging Telescope | In English | → Astronomy |