Christina Aguilera, singer and songwriter

Calcium, symbol for the chemical element (Ca)

Conversation analysis

Civil Affairs, the official name for military units that conduct civil-military operations

Cardiac arrest

Computer Animation (CA)

Catalan language, ISO 639 alpha-2 language code (ca)

Cellular automaton

Air China, IATA airline designator (CA)

Christian anarchist, an adherent of Christian anarchism

Carmelo Anthony, NBA player

Cagliari, capital of the island of Sardinia, Italy (CA)

Carlisle, the United Kingdom postcode for the region in north-western England served by the Carlisle postal sorting office

Cyanoacrylate, superglue

Cary Academy, a North Carolina school

Chartered accountant (CA)

Canadian Alliance, a former Canadian political party

CA, Inc. (formerly known as Computer Associates)

Central America

Armored cruiser, U.S. Navy hull classification symbol, pre 1930 (CA)

Carbonic anhydrase

Chromatic aberration

Heavy cruiser, U.S. Navy hull classification symbol (CA)

Certificate authority (or Certification Authority) (CA)

Conditional access, Conditional Access (Broadcast)

Classic Army, a Hong Kong based manufacturer of airsoft replicas

Chief of Army (Australia)

Cayman Airways, airline

Countryside Alliance, UK

Cannabis Assembly, a UK organisation promoting the religious use of Cannabis

Creative Assembly, PC Game Developer

Conscientious Arsonists, Greek terrorist organization

Crédit Agricole

Chemical Abstracts, an index of the scientific literature in chemistry and related fields, supplemented by abstracts

Cultural algorithm (CA)

C&A stores

Cricket Australia

Circa (ca.)

Channel America, a defunct US television network

Cocaine Anonymous

Cycling Australia

Controlled atmosphere

Class A

Central Administration

Citizens' Alliance, a political party in Trinidad and Tobago

Catamarca, a province in Argentina

Bureau of Consular Affairs, a division of the US Department of State

California (United States postal abbreviations)

Canada, ISO 3166, FIPS Pub 10-4 and obsolete NATO digram (CA)

.ca is also the ccTLD for Canada

Cancer/Carcinoma