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 •
Cost Index (CI), the ratio of time cost to fuel cost, used to calculate the cruising speed of an airliner ==Television==