AC

AC, A.C., A/C, or Ac often refers to:
 * Air conditioning, often abbreviated as A/C
 * Alternating current, a type of electrical current in which the current repeatedly changes direction

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

Gaming

 * Ace Combat, a series of combat flight simulator games
 * Animal Crossing, a series of community simulation games
 * Anonymous;Code, a visual novel in the Science Adventure series
 * Another Code, a series of adventure games
 * Armored Core, a series of mecha-based third person shooter games
 * 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
 * Astral Chain, an action-adventure hack and slash game
 * Armor Class, a combat-related parameter in the Dungeons & Dragons role playing game system
 * A.C., a character in Fortnite: Save the World

Music

 * A.C. Newman, solo stage name for Canadian musician Carl Newman
 * AC/DC, an Australian rock band formed in Sydney in 1973
 * Adult contemporary music, a genre description used mainly in radio broadcasting
 * Adult Contemporary (chart)
 * 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
 * Asianovela Channel, a defunct Filipino TV channel

Businesses

 * AC Cars, a British specialist automobile manufacturer
 * AC Spark Plug, Delco, AC-Delco, and ACDelco, automotive parts brands owned by General Motors
 * AC Hotels, a hotel chain owned by Marriott International
 * AC Restaurants, a hotel and restaurant chain in the Benelux
 * Air Canada, the flag carrier and largest airline of Canada (IATA code AC)
 * Allis-Chalmers, a former industrial conglomerate
 * Anderson, Clayton and Company, former American cotton trading firm
 * Associated Content, an online publisher and distributor of original content
 * Ayala Corporation, a holding company (Philippine Stock Exchange symbol AC)

Politics

 * Action Congress, a political party in Nigeria
 * Advisory Council on Youth, a non-governmental decision-making body in the Council of Europe.
 * 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 – 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
 * Anthrocon, the second largest furry convention in the world, held in Pittsburgh, Pennsylvania, US
 * Audit Commission (Hong Kong), a government department in Hong Kong Special Administrative Region
 * Aryan Circle, a white supremacist, Neo-Nazi prison gang spread throughout many U.S. correctional facilities

People

 * AC Bonifacio, a Philippine-Canadian actress, singer and dancer
 * 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)
 * Antigua and Barbuda, obsolete two-letter FIPS and NATO codes
 * 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
 * Aviation Cadet, a military rank sometimes written as A/C

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
 * Adenocarcinoma, a type of cancerous tumor
 * Allergic conjunctivitis, inflammation of the conjunctiva

Chemistry

 * Acetyl, a functional group in chemistry
 * Actinium, symbol Ac, a chemical element
 * Hydrogen cyanide, also called as AC in chemical weapon term

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
 * Arithmetic coding, a form of entropy encoding used in lossless data compression
 * alternating component a.k.a. AC coefficient in discrete cosine transform
 * IEEE 802.11ac, a wifi standard using 5 GHz, 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

 * Air conditioning, technologies for altering the temperature and humidity of air
 * 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
 * Asphalt concrete, a type of road or path surfacing
 * Average cost, in economics
 * Axiom of choice, a mathematical concept in set theory
 * A US Navy hull classification symbol: Collier (AC)

Other uses

 * Ac (rune) (ᚪ), a rune of the Anglo-Saxon fuþorc and a continuation of the Elder Fuþark ansuz
 * A.C. Milan, an Italian football club based in the city of Milan
 * 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"
 * Antichrist, a Biblical prophecy about one who will oppose Jesus Christ and substitute himself in Christ's place
 * Appeal Cases, or A.C., a UK law reporter covering decisions of the House of Lords, Supreme Court, Privy Council, and Court of Appeal
 * Armor Class, a common property in role playing games used to determine the amount of armor a character has
 * Army Corps, an operational formation, sometimes known as a field corps, which consists of two or more divisions
 * Atlantic College, an international IB Diploma Programme residential Sixth Form College in the Vale of Glamorgan in Wales
 * Auto Calesa, a war-time short-body version of the Philippine jeepney