| ChJL | Chinese Journal of Lasers | In English | → Serial publications, periodicals → Optics |
| ChJNP | Chinese Journal of Nuclear Physics | In English | → Serial publications, periodicals → Nuclear, atomic, and molecular physics |
| ChJPh | Chinese Journal of Physics | In English | → Serial publications, periodicals → Physics |
| ChJPR | Chinese Journal of Polar Research | In English | → Serial publications, periodicals → Earth sciences |
| ChJS | Chinese Journal of Semiconductors | In English | → Serial publications, periodicals → Physics |
| ChJSS | Chinese Journal of Space Science | In English | → Serial publications, periodicals → Astronomy → Spaceflight engineering, astronautics |
| CHL | Certified Hardware List | In English | → Software |
| CHLA | Canadian Health Libraries Association = ABSC | Association des Bibliothèques de la Santé du Canada | In French |
In English | → Libraries → Associations → Medicine |
| CHNM | Center for History and New Media | In English | → Newspapers, journalism → History |
| ChPh | Chemical Physics | In English | → Serial publications, periodicals → Chemistry → Physics |
| ChPhL | Chinese Physics Letter | In English | → Serial publications, periodicals → Physics |
| ChPhy | Chinese Physics | In English | → Serial publications, periodicals → Physics |
| CHR | Cooper-Harper Rating | In English | |
| CHRE | Council for Healthcare Regulatory Excellence | In English | → Medicine |
| CHS | Committee on Hemispheric Security = CSH | Comisión de Seguridad Hemisférica | In Spanish = CSH | Comissão de Segurança Hemisférica | In Portuguese |
In English | → International relations |
| ChSAJ | Chinese Society of Astronautics Journal | In English | → Serial publications, periodicals → Astronomy → Spaceflight engineering, astronautics |
| ChSBu | Chinese Science Bulletin | In English | → Serial publications, periodicals → Mathematics and natural sciences |
| CHSF | Cargo Hydrazine Service Facility | In English | |
| ChSMJ | Chinese Society of Mechanical Engineers Journal | In English | → Serial publications, periodicals → Mechanical engineering |
| ChSRv | Chemical Society Reviews | In English | → Serial publications, periodicals → Chemistry |
| ChSST | Chinese Space Science Technology | In English | → Serial publications, periodicals → Astronomy → Spaceflight engineering, astronautics |
| CHT | Catalog of Hittite Texts = CTH | Catalogue des Textes Hittites | In French |
In English | → Bibliography → Libraries → Language, linguistics, literature |
| CHTML | Compact HyperText Markup Language | In English | → Programming languages → Telecommunications |
| CHUS | Chinese Historians in the United States | In English | → Organizations and associations → History |
| CHW | Command Header Word | In English | |
| CHX | Cabin Heat Exchanger | In English | |
| CHX | Condensing Heat Exchanger | In English | |
| CI | Configuration Item | In English | |
| CI | Continuous Interlock | In English | |
| CI | Contract Initiation | In English | → 3474 |
| CI | Course Invalid | In English | |
| CI | Crew Interface | In English | |
| CI | Configuration Inspection | In English | |
| CI | Color Interior Film | In English | |
| CI | Certification Inspection | In English | |
| CI | Center Of Impact | In English | |
| CI | Cast Iron | In English | |
| CI | Competitive Intelligence | In English | |
| CIA | Controller Interface Assembly | In English | → Human-computer interaction |
| CIA | Control Interface Assembly | In English | → Human-computer interaction |
| CIA | Configuration Identification Accounting | In English | |
| CIA | Central Intelligence Agency | In English | → Central administration → Polemology |
| CIAP | Climatic Impact Assessment Program | In English | |
| CIAS | Central and Inner Asia Seminar | In English | → Area studies |
| CIB | Control Interface Block | In English | → Human-computer interaction |
| CIB | Change Impact Board | In English | |
| CIB | Change Implementation Board | In English | |
| CiBAA | Circular of the British Astronomical Association | In English | → Serial publications, periodicals → Astronomy |
| CIC | Counselling and Information Centers | In English | |
| CIC | Critical Item Consolidation | In English | |
| CIC | Control and Information Center | In English | |
| CIC | Command Interface Control | In English | → Human-computer interaction |
| CIC | Cargo Integration Contractor | In English | |
| CICC | Cargo Integration Control Center | In English | |
| CICCR | Configuration Information Control Center Requirement | In English | |
| CICONA | Comissão Interparlamentar Centro-americana contra a Corrupção e o Narcotráfico = CICONA | Comisión Interparlamentaria Centroamericana contra la Corrupción y la Narcoactividad | In Spanish |
In English | → Parliaments, representation → Police |
| CICP | Cambodian Institute for Cooperation and Peace (www.cicp.org.kh) | In English | → Research institutes → Democracy → Internal policy → International relations |
| CICU | Communication Interface Control Unit | In English | |
| CICU | Computer Interface Conditioning Unit | In English | → Human-computer interaction |
| CID | Cable Interconnect Diagram | In English | |
| CID | Charge Injection Device | In English | |
| CID | Computer Interface Device | In English | → Human-computer interaction |
| CIDA | Canadian International Development Agency = ACDI | Agence Canadienne de Développement International | In French |
In English | → Central administration → Development |
| CIDL | Configuration Item Data List | In English | |
| CIDR | Critical Intermediate Design Review | In English | |
| CIDSC | Contractor In-House Data Support Capability | In English | |
| CIE | Cargo Integration Equipment | In English | |
| CIE | Communications Interface Equipment | In English | → Human-computer interaction → Telecommunications |
| CIE | Cyprus Institute of Energy | In English | → Energy economics |
| CIER | Chung-Hua Institution for Economic Research | In English | → Economics |
| CIESIN | Center for International Earth Science Information Network | In English | → Research institutes → Earth sciences |
| CIF | Central Information Facility | In English | |
| CIF | Central Instrumentation Facility | In English | |
| CIFA | Committee for Inland Fisheries of Africa | In English | → Organizations and associations → Fishing, hunting |
| CIFTA | Inter-American Convention against the Illicit Manufacturing of and Trafficking in Firearms, Ammunition, Explosives, and Other Related Materials = CIFTA | Convención Interamericana contra la Fabricación y el Tráfico Ilícitos de Armas de Fuego, Municiones, Explosivos y Otros Materiales Relacionados | In Spanish = CIFTA | Convention Interaméricaine contre la Fabrication et le Trafic illicites d'Armes à feu, munitions, explosifs et autres matériels connexes | In French = CIFTA | Convenção Interamericana contra a Fabricação Ilícita e o Tráfico de Armas de Fogo, Munições, Explosivos, e Outros Materiais Relacionados | In Portuguese |
In English | → International relations → Military engineering |
| CIG | Connector Integrity Group | In English | |
| CIG | Connector Integration Group | In English | |
| CIG | Compound Interlace Grating | In English | |
| CIG | Communications and Interface Group | In English | → Human-computer interaction → Telecommunications |
| CIG | Cable Integrity Group | In English | |
| CIGOS | Canadian Interest Group on Open Systems | In English | → Organizations and associations → Computer science |
| CIHR | Canadian Institutes of Health Research (www.cihr.ca) = IRSC | Instituts de recherche en santé du Canada | In French |
In English | → Research institutes → Biological sciences → Medicine |
| CIHTS | Central Institute of Higher Tibetan Studies | In English | |
| CII | Change Installation Instruction | In English | |
| CII | Configuration Item Identifier | In English | |
| CIIR | Catholic Institute for International Relations | In English | → Roman catholic church → International relations |
| CIIT | Chemical Industry Institute of Toxicology | In English | → Research institutes → Pharmacology, toxicology → Chemical technology |
| CIJB | Cradle Interface Junction Box | In English | |
| CIKTN | Chemistry Innovation Knowledge Transfer Network | In English | → Organizations and associations → Chemistry |
| CIL | Critical Items List | In English | |
| CILT | Center for Information on Language Teaching and Research (www.cilt.org.uk) | In English | → Organizations and associations → Education → Language, linguistics, literature |
| CIM | Comisión Interamericana de Mujeres (www.oas.org/cim/) = IACW | Inter-American Commission of Women | In English = CIF | Commission Interaméricaine des Femmes | In French = CIM | Comissão Interamericana de Mulheres | In Portuguese |
In English | → Organizations and associations → Feminism |
| CIM | Computer-Integrated Manufacturing | In English | → Hardware → Electronics |
| CIM | Computer Input Multiplexer | In English | → Computer science |
| CIMP | Commision Internationale de Microflore Paléozoique | In English | → Organizations and associations → Paleobotany, palynology → Botany |
| CIMR | Cambridge Institute for Medical Research | In English | → Research institutes → Medicine |
| CIMS | Consolidated Information Management System | In English | |
| CIN | Center Information Network | In English | |
| CIN | Change Identification/Identifier Number | In English | |
| CINC | Commander-In-Chief | In English | |
| CINCAD | Commander-In-Chief, Air Defense | In English | → 358 |
| CINCNET | Commander-In-Chief Network | In English | |
| CINCNORAD | Commander-In-Chief, North American Aerospace | In English | |
| CINCSAC | Commander-In-Chief, Strategic Air Command | In English | |
| CINCSBL | Commander-In-Chief, Space-Based Laser | In English | |
| CINDE | Costa Rican Investment & Development Board (www.cinde.or.cr) | In English | → 33972 |
| CIO | Chief Information Officer | In English | |
| CIP | Cast-Iron Pipe | In English | |
| CIP | Change Implementation Plan | In English | |
| CIP | Communications Interface Processor | In English | → Human-computer interaction → Telecommunications |
| CIP | Control and Interface Panel | In English | → Human-computer interaction |
| CIP | Center for Islamic Pluralism | In English | → Islam |
| CIPA | Center for International Programs Abroad | In English | → International relations |
| CIPAM | Centre for Industrial Management, Polish Academy of Sciences | In English | → Industry, industrial policy |
| CIPP | Cured-In-Place Piping | In English | → Environmental technology, water supply, waste management |
| CIPSG | Canadian Information Processing Society Graphics Interface | In English | → Serial publications, periodicals |
| CIR | Critical Item Report | In English | |
| CIR | Configuration Inspection Report | In English | |
| CIR | Cargo Integration Review | In English | |
| CIR-CE | Cooperation in Innovation and Research with Central and Eastern Europe | In English | |
| CIRCE | Confusion-limited Infrared Cosmology Explorer | In English | → Cosmology → Spaceflight engineering, astronautics |
| CIRD | Cargo Integration Review Dry Run | In English | |
| CIRHS | Critical Items and Residual Hazards List | In English | |
| CIRIA | Construction Industry Research and Information Association | In English | → Organizations and associations → Building |
| CIRM | Celestial Infrared Mapping | In English | |
| CIRM | Celestial Infrared Measurements | In English | |
| CIRM | California Institute for Regenerative Medicine | In English | → Biotechnology → Medicine |
| CIRRIE | Center for International Rehabilitation Research Information and Exchange (http://cirrie.buffalo.edu) | In English | |
| CIRRIS | Cryogenic Infrared Radiance Instrumentation for Shuttle | In English | → Spaceflight engineering, astronautics |
| CIRRIS | Cryogenic Infrared Radiance Instrument for Shuttle | In English | → Spaceflight engineering, astronautics |
| CIRSE | Cardiovascular and Interventional Radiological Society of Europe | In English | → Cardiology |
| CIS | Communication Interface System | In English | → Human-computer interaction |
| CIS | Contractor's Information Submittal | In English | → 3474 |
| CIS | Change Impact Summary | In English | |
| CIS | Central Integration Site | In English | |
| CIS | Cargo Integration Schedule | In English | |
| CIS | Commonwealth of Independent States = PNM | Persemakmuran Negara-Negara Merdeka | In Indonesian |
In English | → International relations |
| CIS | Certification & Information Security Services GmbH | In English | |
| CIS | Common Implementation Strategy | In English | |
| CIS | Community Innovation Survey | In English | → Engineering, technology |
| CIS | Contact Image Sensor | In English | → Electronics |
| CISAB | Center for the Integrative Study of Animal Behavior | In English | → Organizations and associations → Zoology |
| CISB | Centre for Integrated Structural Biology | In English | → Biological sciences |
| CISC | Complex Instruction Set Computer | In English | → Hardware |
| CISCOW | Centre for Interdisciplinary Research on Islam in Contemporary World | In English | → Islam |
| CISO | Chief Information Security Officer = RSSI | Responsable de la Sécurité des Systèmes d'Information | In French |
In English | → Computer science |
| CISS | Centaur Integrated Support Structure | In English | |
| CIT | CAP Initialization Tape | In English | |
| CIT | Critical Item Tag | In English | |
| CIT | California Institute of Technology | In English | → Engineering, technology |
| CITAS | China In Time And Space | In English | |
| CITE | Cargo Integration Test Equipment | In English | |
| CITES | Convention on International Trade in Endangered Species of Wild Fauna and Flora | In English | → International relations → Nature |
| CITL | Community Independent Transaction Log | In English | |
| CITM | Chubu Institute of Technology, Memoirs | In English | → Serial publications, periodicals → Applied sciences, technology |
| CITS | Central Integrated Test System | In English | |
| CITS | Croatian Information Technology Society | In English | → Organizations and associations → Computer science → Telecommunications |
| CIU | Controller Interface Unit | In English | → Human-computer interaction |
| CIU | Computer Interface Unit | In English | → Human-computer interaction |
| CIU | Communication Interface Unit | In English | → Human-computer interaction → Telecommunications |
| CiUO | Circular of the Union Observatory Johannesburg | In English | → Serial publications, periodicals → Astronomy |
| CIVT | Cargo Interface Verification Test | In English | |
| CIVU | Cargo Integration Verification Unit | In English | |
| CIWG | Cargo Integration Working Group | In English | |
| CJAS | Copenhagen Journal of Asian Studies | In English | → Serial publications, periodicals → Language, linguistics, literature → Geography, biography, history |
| CJAS | Canadian Journal of African Studies | In English | → Language, linguistics, literature → Geography, biography, history |
| CJChE | Canadian Journal of Chemical Engineering | In English | → Serial publications, periodicals → Chemical technology → Chemistry |
| CJEC | Court of Justice of the European Communities = CJCE | Cour de Justice des Communautés Européennes | In French = TJCE | Tribunal de Justícia de les Comunitats Europees | In Catalan = LICE | Llys Cyfiawnder Ewrop | In Welsh = ΔΕΚ | Δικαστήριο των Ευρωπαϊκών Κοινοτήτων | In Greek = EuGH | Europäischer Gerichtshof | In German = JKEK | Justica Kortumo de Eŭropaj Kortumoj | In Esperanto = TJCE | Tribunal de Justicia de las Comunidades Europeas | In Spanish = CGCE | Corte di Giustizia delle Comunità Europee | In Italian = HvJEG | Hof van Justitie van de Europese Gemeenschappen | In Dutch = EBTT | Europos Bendrijų Teisingumo Teismas | In Lithuanian |
In English | → Law, jurisprudence → European Union |
| CJECE | Canadian Journal of Electrical Computer Engineering | In English | → Serial publications, periodicals → Computer science → Electrical engineering |
| CJFLCC | Coalition Joint Forces Land Component Command | In English | → Military affairs |
| CJK | China/Japan/Korea | In English | → Geography |
| CJKI | (The) Chinese, Japanese, and Korean Dictionary Institute | In English | → Dictionaries → Linguistics |
| CJLTP | Chinese Journal of Low Temperature Physics | In English | → Serial publications, periodicals → Physics |
| CJMat | Canadian Journal of Mathematics | In English | → Serial publications, periodicals → Mathematics |
| CJNE | Canadian Journal of Native Education | In English | → Serial publications, periodicals → Education |
| CJNEAS | Centre for Japanese and North East Asian Studies | In English | → Language, linguistics, literature → Geography, biography, history |
| CJPP | Canadian Journal of Physiology and Pharmacology | In English | → Serial publications, periodicals → Physiology → Pharmacology, toxicology |
| CJS | Center for Japanese Studies | In English | → Language, linguistics, literature → Geography, biography, history |
| CJS | Center for Jewish Studies | In English | → Judaism → Language, linguistics, literature → Geography, biography, history |
| CJSA | China Judaic Studies Association | In English | → Associations → Judaism → Language, linguistics, literature → Geography, biography, history |
| CJSC | Closed Joint Stock Company = ЗАО | Закрытое Акционерное Общество | In Russian = ZAO | Zakrytoe Akcionernoe Obščestvo | In Russian |
In English | → Economics |
| CKC | Continental Kennel Club | In English | → Organizations and associations |
| CKRA | Cape Kennedy Reference Atmosphere | In English | |
| CKS | Center for Korean Studies | In English | → Language, linguistics, literature → Geography, biography, history |
| CL | Closed Loop | In English | |
| CL | Coefficient Of Lift | In English | |
| CL | Confidence Level | In English | |
| CLA | Conjugated Linoleic Acid | In English | → Biochemistry, biophysics |
| CLA | Cantonese Language Association (http://asiane.byu.edu/cla/) | In English | → Associations → Education → Language, linguistics, literature |
| CLAES | Cryogenic Limb Array Etalon Spectrometer | In English | → Analytical chemistry |
| CLAH | Conference on Latin American History | In English | → Organizations and associations → History |
| CLAMP | Climate Leaf Analysis Multivariate Program | In English | → Meteorology, climatology → Paleobotany, palynology |
| CLAS | Computerized Loads Analysis System | In English | |
| CLASS | Chinese Language Association for Secondary-Elementary Schools | In English | → Associations → Education → Linguistics |
| CLASS | Chinese Language Association for Secondary School (www.classk12.org) | In English | → Associations → Education → Language, linguistics, literature |
| CLC | Change Letter Control | In English | |
| CLC | Computer Liaison Committee | In English | |
| CLC | Canadian Labour Congress = CTC | Congrès du Travail du Canada | In French |
In English | → Organizations and associations → Labour, labour economics |
| CLDB | Cell Line Data Base | In English | → Cytology → Biotechnology |
| ClDy | Climate Dynamics | In English | → Serial publications, periodicals → Meteorology, climatology |
|