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Crime Scene Investigation, a term for forensics

CSI: Crime Scene Investigation , a popular television show about forensic scientists

CSI: Miami, a spin-off show of the above

CSI: NY, another spin-off of the above

''CSI: Crime Scene Investigation'' (computer game), a spin-off game

CSI: Dark Motives, a spin-off game

CSI: 3 Dimensions of Murder, the third game in the series

Caesium iodide or cesium iodide (strictly CsI), an ionic compound used in chemistry

Chlorosulfonyl isocyanate, a reagent in organic synthesis

Centre de Sociologie de l'Innovation, a research center in France

Coral Sea Islands, a group of small uninhabited tropical islands and reefs in the Coral Sea, northeast of Queensland, Australia

Chhatrapati Shivaji International Airport (formerly known as Sahar Airport), an airport in Mumbai, India

Canadian Securities Institute, the educational body of the Investment Dealers Associations of Canada

CSI, one of several religious organizations:

Church of South India, a union of protestant Christian churches spread over South India

Church of Scientology International, the largest organization devoted to the practice and the promotion of the Scientology belief system

Christian Surfers International, an evangelical mission agency which seeks to convert surfers to Christianity through the sport of surfing

Christian Schools International, an organization that supports Christian school teachers who want Bible-based textbooks for their classrooms

Scouting Ireland (CSI), a world organization of the Scout Movement

Cite Scolaire Internationale de Lyon, an international highschool in Lyon, France

College of Staten Island, one of the "hybrid colleges" of the City University of New York

Container Security Initiative, an U.S. Customs and Border Protection initiative dealing with the security of cargo containers shipped by sea.

Common System Interface, a future computer bus being planned by Intel

Commission Sportive Internationale, a former part of Fédération Internationale de l'Automobile (FIA) that ruled motorsport, later known as FISA

Complex specified information, a concept intended to formalize a property that singles out patterns that are both specified and complex

Construction Specifications Institute, an organization that maintains and advances the standarization of construction language as pertains to building specifications

Consorzio Suonatori Indipendenti, an Italian band evolved from former punk/art band CCCP

Crime Stoppers International (especially Crimestoppers International Foundation which operates the Crimestoppers programs), the umbrella organization operated by a volunteer board of directors from various Crimestoppers programs

Customer Satisfaction Index, a business term which is used to capture the idea of measuring how satisfied an enterprise's customers are (see also American Customer Satisfaction Index)

Computer Security Institute, a computer organization

CompuServe Inc., the first major commercial online service in the United States

Companion of The Most Exalted Order of the Star of India, an order of chivalry

Control Sequence Introducer, an ANSI escape code

Carbon/Silicon, a rock band