# 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

* CI Financial, Canadian investment management company
* 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
* Cryonics Institute, American nonprofit foundation

## Law and military

* Counterintelligence
* Confidential informant
* Compliance Inspection, a United States Air Force inspection
* Chief inspector, a police rank
* Circle inspector, a junior police rank
* Certificate of identity
* Civilian Internee, a special status of a prisoner during wartime
* Civilian Instructor, an adult volunteer in the British Air Training Corps and Canada Air Cadets

## 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
* Cook Islands, an island-country in the South Pacific Ocean
* Côte d'Ivoire (ISO country code)
* Channel Islands
* Channel Islands of California
* Carbonia-Iglesias, a province in southern Italy
* Central India, region of India, abbreviated CI
** Central India Circuit or C. I. Circuit, a Hindi film distribution circuit comprising parts of Madhya Pradesh (Indian state within central India)

## 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