CI
CI or Ci may refer to:

Business terminology
Commercial invoice
Competitive intelligence
Confidential information
Continual improvement
Corporate identity
Customer intelligence, a discipline in marketing

Businesses and organisations
Academia and education
California State University, Channel Islands
Channel Islands High School
Collegium Invisibile
Confucius Institute

Religion
Josephites of Belgium, a Catholic congregation
Christian Identity
Christian Institute, a British charity which promotes Christian values

Other businesses and organizations
Charity Intelligence Canada
China Airlines (IATA code)
Cigna health services (NYSE symbol)
Consumers International
Cycling Ireland
CI Records, a music record label
Cambria and Indiana Railroad
CANZUK International, organisation which promotes cooperation between Canada, Australia, New Zealand and the United Kingdom
Conservation International, an international environmental non-governmental organization
Communications International, a former global union federation
Communist International
Children International, a non-profit child sponsorship organization

Law and military
Counterintelligence
Confidential informant
Compliance Inspection, a United States Air Force inspection
Chief inspector, a police rank
Certificate of identity
Circle Inspector of Police, a police inspector who is incharge of a police circle in india.
Civilian Internee, a special status of a prisoner during wartime
Civilian Instructor, an adult volunteer in the British Air Training Corps

Places
Ci County, in Hebei, China
Cayman Islands
Chile (FIPS country code, obsolete NATO country code)
Coney Island
Cocos (Keeling) Islands, an external territory of Australia
Côte d'Ivoire (ISO country code)
Channel Islands
Channel Islands of California
Carbonia-Iglesias, a province in southern Italy

Science, technology and mathematics
Biology and medicine
cI protein, a repressor protein of Enterobacteria phage λ
Cytoplasmic incompatibility, a reproductive system
Cardiac index
Ci protein, Cubitus interruptus -protein
Coital incontinence
Convergence insufficiency
Corpulence index
Cumulative incidence, used as a measure of disease frequency in epidemiology
Cochlear implant
Chemical injury syndrome, an increased sensitivity to common chemicals also called multiple chemical sensitivity.
Chronic illness, a condition that is long-lasting or recurrent
Contraindication

Computing
.ci, the Internet country code top-level domain (ccTLD) for Côte d'Ivoire
Common Interface, for a Conditional Access Module
CI+, Common Interface Plus
Computational intelligence
Configuration item, the fundamental structural unit of a configuration management system
Core Image, non-destructive image processing technology
Continuous integration, a software-engineering practice of merging developer code into a main code base frequently
CodeIgniter, a PHP framework

Earth science
Cirrus cloud
Convective instability

Mathematics
Conditional independence, a type of relation of random variables in probability theory
Confidence interval, an interval estimate of a population parameter used in statistics
101 (number) (in Roman numerals)
Compound interest
Cosine integral (standard mathematical symbols "Ci" and "ci")

Physics
Conical intersection, the location of a discrete degeneracy between two electronic states
Curie (unit) (Symbol: Ci), a measurement of radioactivity named after Marie Curie
Copenhagen interpretation, an interpretation of quantum mechanics
Cubic inch, a unit of volume

Other uses in science and technology
CI group, a type of carbonaceous chondrite meteorite
Carrier interferometry, a radio and optical communication coding technology
Chemical ionization, a technique used in mass spectrometry
Configuration interaction, a post-Hartree–Fock method used in computational chemistry
Contextual inquiry,  a user-centered design research method
Collective intelligence, a subfield of sociology
Colour Index International, a reference database of CI numbers for dyes and pigments
Bavarian C I, a steam locomotive with the Royal Bavarian State Railways
Compression ignition engine, another name for a diesel engine

Television
Canadian Idol, a Canadian television series
Law & Order: Criminal Intent, an American television series
Crime & Investigation Network
Crime & Investigation Network (Australia), Australian cable and satellite network focusing on Crime
Crime & Investigation Network (Europe), a pan-European television channel
Crime & Investigation Network (South East Asia)

Other uses
Ci (poetry), a form of Chinese lyric poetry
Qi, a central concept in several eastern philosophies
Categorical imperative, in philosophy
Colour Index International, a reference database
Comprehensible input
Contact improvisation, a dance technique
CI, postnominal for Companion of the Order of the Crown of India
Ci, a form of the surname Qi, of the Tungusic peoples

See also
C1 (disambiguation)
Cl (disambiguation)