AC, A.C. or Ac may refer to:
- Air conditioning, technologies for altering the temperature and humidity of air
- Alternating current, a type of electrical current in which the current repeatedly changes direction
Arts and entertainment
Gaming
- Ace Combat, a series of combat flight simulator games
- Armor Class, a combat-related parameter in the Dungeons & Dragons role playing game system
- Asheron's Call, a fantasy massively multiplayer online role-playing game
- Assassin's Creed, a series of action-adventure games
- Assetto Corsa, a racing simulator game
Music
- A.C. Newman, solo stage-name for Canadian musician Carl Newman
- Adult contemporary music, a genre description used mainly in radio broadcasting
- Anal Cunt, an American musical group
Other media
- AC Comics, a comic book publisher established in 1969
- A.C. Slater, a fictional character in the American sitcom Saved by the Bell
- After Colony, an alternate timeline in the Gundam metaseries for the universe of Gundam Wing
- AC, the name of the "ultimate computer" in Isaac Asimov's novel The Last Question
Businesses and organizations
Businesses
- AC Cars, a British specialist automobile manufacturer
- AC Restaurants, a hotel and restaurant chain in the Benelux
- Air Canada, the flag carrier and largest airline of Canada (IATA code AC)
- Associated Content, an online publisher and distributor of original content
- Ayala Corporation, a holding company (Philippine Stock Exchange symbol AC)
Political organizations
- Action Congress, a political party in Nigeria
- Alternative for Change (Alternativa por el Cambio), a political party in Nicaragua
- Coast Alliance (Alianza Costeña), a former regional political coalition in Nicaragua
Other organizations
- AC â€" 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
- Ad Council Japan (AC Japan), an organization that distributes Japanese public service announcements
- Athletics Canada, the governing body of athletics in Canada
- Civic Alliance Foundation (Alianţa Civică), a Romanian non-governmental organization
People
- A. C. Green, retired professional basketball player
- A. C. Grayling, British philosopher
- Al Cowlings, retired American football player
Places
- .ac, Internet top-level domain name for Ascension Island
- Aachen, a spa town in North Rhine-Westphalia, Germany
- Acre (state), Brazil
- Aleksandrovac, Serbia (vehicle registration plate code AC)
- Atlantic City, New Jersey, US
Ranks, titles, and awards
- Aelod y Cynulliad, title for Members of the National Assembly for Wales
- Aircraftman, an air forces rank
- Ashoka Chakra (military decoration), India's highest peacetime military decoration
- Assistant Commissioner of Police of the Metropolis, a rank in London's Metropolitan Police
- Companion of the Order of Australia
- First assistant camera or Second assistant camera, in film-making
Science and technology
Biology and medicine
- Acromioclavicular joint (AC joint), the shoulder junction between the scapula and the clavicle
- Adenylate cyclase, a lyase enzyme
- Adriamycin and cyclophosphamide, a chemotherapy regimen used to treat breast cancer
- Ante cibum (ac), Latin for "before meal", commonly seen in medical prescriptions
- Anterior commissure, a bundle of nerve fibers connecting the two temporal lobes of the brain
- Anterior cruciate ligament (AC ligament or ACL), a major ligament in the knee
- Appropriateness criteria, when it is appropriate to perform a medical procedure or service
- Assist control, a former term for continuous mandatory ventilation, a mode of mechanical ventilation
Chemistry
- Acetyl, a functional group in chemistry
- Actinium, a chemical element
Computing and telecommunications
- .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
- AC (complexity), a hierarchy of complexity classes found in circuit complexity
- AC, initialism of access control
- Artificial consciousness, a field related to artificial intelligence and cognitive robotics
- Authorization certificate or attribute certificate, a digital permission to use a service or resource
- 802.11ac, a wifi standard using 5GHz, released in Dec 2013
Meteorology
- Altocumulus, a medium level cloud type
- Anticipated convection, convective outlooks issued by the U.S. National Weather Service
Other uses in science and technology
- Across corners (A/C), a measure of external diameter of hexagonal nuts
- Alternating current, a type of electric current
- AC power, a net transfer of energy over a complete cycle of the alternating current waveform
- Average cost, in economics
- Axiom of choice, a mathematical concept in set theory
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
- Ante Christum or A.C., a Latin term meaning "before Christ"
- Anthrocon, the largest furry convention in the world, held in Pittsburgh, Pennsylvania, US
- Asphalt concrete, a type of road or path surfacing
