California Academy of Sciences, a major natural history museum and center for scientific research
Career Academies of Seminole, a program run by Pinellas County Schools in Florida
Casablanca American School, a coed private prep school in Casablanca, Morocco
Casualty Actuarial Society, a professional society of actuaries in the United States
Centre for Astrophysics and Supercomputing, a research center at Swinburne University in Australia
Chemical Abstracts Service, a division of the American Chemical Society which produces bibliographic and chemistry databases
Chinese Academy of Sciences, the national academy for the natural sciences of China
Combined Associated Schools, an association of private schools in Sydney, Australia
Contemporary Art Society, UK
Contemporary Art Society (Australia)
Contemporary Art Society, Adelaide, later the Contemporary Art Centre of South Australia
Contemporary Arts Society, Canada
Court of Arbitration for Sport, an international arbitration body set up to settle disputes related to sports
Children's Aid Society, a private charity in New York City
Children's Aid Society (Ontario), a Canadian government organization
Christchurch Adventist School, a Seventh-day Adventist school in New Zealand
Civil Aid Service, a Hong Kong Civil Aid agency
Cinema Audio Society, an association of sound professionals in the motion picture and television industry
Council for the Advancement of Standards in Higher Education, a consortium of professional student development organizations in higher education
Connecticut Association of Schools, the governing body for secondary school athletics and other competitions in Connecticut, US
Czech Academy of Sciences, formerly Academy of Sciences of the Czech Republic
Český atletický svaz, Czech Athletics Federation
Computing
CAS latency (column address strobe or column address select), a latency in reading computer memory
Central Authentication Service, a single sign-on protocol
Cloud Analytic Services, a server that provides the cloud-based, run-time environment for data management and analytics with SAS (software)
Code Access Security in the Microsoft .NET framework
Compare-and-swap, a special CPU instruction, an atomic instruction used in multithreading to achieve synchronization
Computer algebra system, a software program that facilitates symbolic mathematics
Conditional access system, a technology used in set-top boxes to allow conditional viewing of TV channels
Content-addressable storage, a data storage mechanism
Copyright Alert System, also known as the 'six strikes' program
Cycle-accurate simulator, a computer program that simulates a microarchitecture in a cycle-accurate manner
Science and medicine
Calcium sulfide (CaS), a chemical compound
Coronary artery spasm (CAS)
Carotid artery stenting, endovascular surgery of the carotid artery
Cassiopeia (constellation) (Cas), standard astronomical abbreviation
Cells Alive System
Chemical Abstracts Service, a division of the American Chemical Society which produces bibliographic and chemistry databases
CAS Registry Number, unique numerical identifiers for chemical substances
Cognitive Assessment System, an academic assessment test given to children
Complex adaptive system, special cases of complex systems
Computer Aided Surgery (journal)
Computer-assisted surgery, use computer technology in surgery
Critical animal studies, an interdisciplinary field in the humanities and social sciences
Critical autism studies
Hartley kernel, which also is known as the cosine and sine function
Cis-abienol synthase, an enzyme
CRISPR-associated (Cas) proteins, involved in the prokaryotic immune system and genome editing
CAS parameters, an image analysis method typically used in astronomy
Entertainment and sports
Calling All Stations, the fifteenth and final studio album by Genesis
Cigarettes After Sex, an American ambient pop band
Classic Arts Showcase, an American television channel promoting the fine arts
Cowboy action shooting, a competitive shooting sport
Military
Chief of the Air Staff, the professional head of the air force in some Commonwealth nations
Close air support, a military tactic whereby aircraft are utilized to support friendly forces
Combat armor suit, a specialized suit that provides powered armor
Cost Accounting Standards, accounting requirements for larger defense and government contractors (United States)
Aerospace
Calibrated airspeed, the airspeed shown by an airspeed indicator
Covenant Aviation Security, LLC, a company that provides security services to the aviation industry
Crew-alerting system, the cockpit computer that issues system warnings to pilots
Casablanca–Anfa Airport (IATA code)
Transport
Castleton railway station, Manchester, England (National Rail station code)
Chicago, Attica and Southern Railroad, a former line in the American states of Indiana and Illinois
Other uses
Certificate of Advanced Study, a postgraduate certificate
Channel-associated signaling, in telecommunications
Citizens Advice Scotland, the umbrella organisation for Citizens Advice Bureaux in Scotland
Clark Ashton Smith (1893–1961), American author and artist
Collision avoidance system, an automobile safety system
Controlled American source, a placeholder term used by the Central Intelligence Agency in classified documents to avoid disclosure of specific locations, operations, activities, or individuals
Controlled atmosphere stunning, a method for slaughtering animals
Creativity, activity, service, the community service aspect of the International Baccalaureate Diploma Programme