AC

AC, A.C. or Ac may refer to:

• Air conditioning (often referred to as aircon, AC or A/C), the process of altering the properties of air (primarily temperature and humidity) to more favourable conditions
• Alternating current, a type of electrical current where the current repeatedly changes direction
• Air Canada, the flag carrier and largest airline of Canada by IATA code

Computing

• AC (complexity), a hierarchy of complexity classes found in circuit complexity
• Authorization certificate or attribute certificate, a digital permission to use a service or resource
• .ac, Internet top-level domain name for Ascension Island
• .ac (second-level domain), Internet second-level domain used to denote academic institutions in many countries
• Acceptance Criteria, a defined set of criteria used for doing Acceptance testing

Entertainment

• AC Comics, a comic book publisher established in 1969
• A.C. Newman, solo stage-name for Canadian musician Carl Newman
• A.C. Slater, character in the American sitcom Saved by the Bell
• "AC radio," Adult contemporary music, a genre description used mainly in radio broadcasting
• After Colony, an alternate timeline in the Gundam metaseries for the universe of Gundam Wing
• American Capitalist, the third studio album from American rock band 5FDP
• Anal Cunt, an American musical group
• Armor Class, a combat-related parameter in the Dungeons & Dragons role playing game system
• AC, the name of the ultimate computer at the end of time in Isaac Asimov's The Last Question

Video games

• Ace Combat, a series of combat flight simulator games
• Armored Core, a series featuring the eponymous robotic fighter under the player's control
• Asheron's Call, a fantasy massively multiplayer online role-playing game

Job titles and ranks

• Aelod y Cynulliad, the title for Members of the National Assembly for Wales
• Aircraftman, an air forces rank
• Assistant Commissioner of Police of the Metropolis, a rank in London's Metropolitan Police
• AC, a person appointed Companion of the Order of Australia
• First assistant camera or Second assistant camera

Organizations

• AC Cars, a British specialist automobile manufacturer
• AC – The Danish Confederation of Professional Associations, an umbrella organisation for several Danish trade unions
• AC Transit, a regional public transit agency in the San Francisco Bay Area
• AC Restaurants, Hotel and restaurant chains in the Benelux
• Action Congress, a political party in Nigeria
• Ad Council Japan (AC Japan), an organization that distributes Japanese public service announcements
• Air Canada, the flag carrier and largest airline of Canada by IATA code
• Alternative for Change (Alternativa por el Cambio), a political party in Nicaragua
• Associated Content, an online publisher and distributor of original content
• Athletics Canada, the governing body of athletics in Canada
• Ayala Corporation (Philippine Stock Exchange symbol), a holding company
• Civic Alliance Foundation (Alianţa Civică), a Romanian non-governmental organization
• Coast Alliance (Alianza Costeña), a former regional political coalition in Nicaragua

People

• A. C. Green, retired professional basketball player
• A. C. Grayling, British philosopher
• Aaron Carter, American musician

Places

• Aachen, a spa town in North Rhine-Westphalia, Germany
• Acre (state), a state in Brazil
• Atlantic City, New Jersey, a city in New Jersey, United States
• Aleksandrovac, Serbia, vehicle registration plate code

Science and technology

• Acetyl, a functional group in chemistry
• Actinium, a chemical element
• Across corners (A/C), a measure of hexagonal nut external diameter
• Alternating current, a type of electric current
  • AC power, a net transfer of energy over a complete cycle of the alternating current waveform
• Altocumulus, a medium level cloud type
• Adenylate cyclase, a lyase enzyme
• Anticipated convection, convective outlooks issued by the U.S. National Weather Service
• Artificial consciousness, a field related to artificial intelligence and cognitive robotics
• Axiom of choice, a mathematical set theory concept

Medicine

• Acromioclavicular joint (AC joint), the shoulder junction between the scapula and the clavicle
• Ante cibum (ac), before meal, commonly used in writing prescriptions
• Anterior commissure
• Anterior cruciate ligament (AC ligament or ACL), a major ligament in the knee
• Appropriateness criteria (AC), when it is appropriate to perform a medical procedure or service
• Arterial catheter (AC)
• Chemotherapy regimens, adriamycin and cyclophosphamide, a chemotherapy regimen used to treat breast cancer
• Assist control, a former term for continuous mandatory ventilation, a mode of mechanical ventilation

Other uses

• Ac (rune) (ᚪ), a rune of the Anglo-Saxon fuþorc and a continuation of the Elder Fuþark ansuz
• Acre, a unit of area with the symbol ac
• Advisory circular, a publication to provide guidance for compliance with airworthiness regulations
• Appeal cases
• Anarcho-capitalism, a form of free-market anarchism
• Ante Christum or A.C., a Latin term meaning "before Christ"
• Anthrocon, the largest furry convention in the world held in Pittsburgh, Pennsylvania
• Ashoka Chakra (military decoration), India's highest peacetime military decoration
• Assessment center, a process to evaluate candidates for a job
• Average cost, in economics
• Asphalt concrete, a type of road / path surfacing