CI

CI or Ci, but not C I or C.I, may refer to:

Business

Ci County, in Hebei, China
Central Islip, New York
Cayman Islands
Chile, FIPS country code and obsolete NATO country code digram
Cocos Island, off the Republic of Costa Rica
Coney Island
Cocos (Keeling) Islands, an external territory of Australia
Christmas Island, an external territory of Australia
Kiritimati, another island by the name of "Christmas Island" in the Pacific Ocean
Côte d'Ivoire, ISO country code digram
- .ci, the Internet country code top-level domain (ccTLD) for Côte d'Ivoire
The IATA airline designator for China Airlines (Taiwan ROC)
Channel Islands
Channel Islands of California
Qi, in Tongyong Pinyin
Carbonia-Iglesias, a province in southern Italy

Cardiac index
Ci protein, Cubitus interruptus -protein
Convergence insufficiency
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

Chemical ionization
Configuration interaction, a post-Hartree–Fock method used in computational chemistry
Conservation International, an international environmental non-governmental organization

CodeIgniter, a PHP framework (see EllisLab#CodeIgniter)
Common Interface for a Conditional Access Module
Computational intelligence
CI+, Common Interface Plus
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

Color index
Conical intersection, the location of a discrete degeneracy between two electronic states
Curie (Symbol: Ci). A measurement of radioactivity named after Marie Curie
Copenhagen Interpretation, an interpretation of Quantum Mechanics.

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 (in Roman numerals)
Compound interest (mathematics)
cubic inch, a unit of volume used almost exclusively in the United States of America
Cosine integral (standard mathematical symbols "Ci" and "ci")

Canadian Idol, the Canadian television series.
Law & Order: Criminal Intent, the television series.
Crime & Investigation Network
- Crime & Investigation Network (Australia), Australian cable and satellite network focusing on Crime.
- Crime & Investigation Network (UK), United Kingdom cable and satellite network focusing on Crime
- Crime & Investigation Network (South East Asia)