ca (not comparable)
- Abbreviation of circa#English|circa.
- 2004 During glacial times, a stretch of level plain joined Australia with New Guinea and enabled humans to walk into Australia. That plain flooded to form the Gulf of Carpentaria, between ca 12,000 and 10,000 ybp. - Wikipedia article on Deluge (mythology)
- Abbreviation of California#English|California, a state of the United States of America.
- Abbreviation of Canada#English|Canada, a country in North America.
- (Canada, politics) Initialism of Canadian Alliance, Conservative-Reform Alliance Party, Reform-Conservative Alliance Party
- Initialism of Computer Associates, an American software company.
- (computing) cellular automata
- The new CA is a modification of Fredkin's earlier SALT architecture in which every cell is identified as either even or odd - as in sodium and chlorine in a salt crystal hence the name. The state of each cell is either up or down and the development rule simple takes account of states of odd and even neighbours. The up-date at each time step simply takes the form of a swap of the states of diagonally related cells. SALT CAs are reversible and capable of universal computation and are conjectured to be capable of universal construction in the sense of Von Neumann.
- (computing) Initialism of certificate authority
- (US, nautical) armored cruiser, a type of warship
- (US, nautical) heavy cruiser, a variant of the cruiser type of warship
- (US, military) civil affairs, a military occupational specialty or branch
- (organic compound) cyanoacrylate
- (Scotland, Canada, AU, NZ, South Africa, accounting) Initialism of chartered accountant
- (Japan) Initialism of cabin attendant
- Central Authority
- French: CA