AA, Aa, Double A, or Double-A may refer to:

Arts, entertainment and media

* ''

America's Army ''America's Army'' is a series of first-person shooter video games developed and published by the U.S. Army, intended to inform, educate, and recruit prospective soldiers. Launched in 2002, the game was branded as a strategic communication device ...

'', a 2002 computer game published by the U.S. Army * ''

Ancient Anguish ''Ancient Anguish'', abbreviated ''AA'', is a fantasy-themed MUD, a text-based online role-playing game. Founded in 1991 by Balz "Zor" Meierhans and Olivier "Drake" Maquelin, it opened to the public on February 2, 1992. It is free-to-play, but has ...

'', a computer game in existence since 1992 *

Aa! was a Japanese girl group in Hello! Project, formerly made up of leader and Morning Musume member Reina Tanaka, Miyabi Natsuyaki and Airi Suzuki, two Hello! Project Kids. History The group's name was chosen by producer and writer Tsunku to rep ...

, a J-Pop musical group * Double-A (band), stylised as AA, South Korean boy band * ''Aa'' (album), a 2016 album by Baauer *

AA (song) "AA" is a song by American country music singer Walker Hayes. It was released on November 19, 2021 as the third single from his third studio album '' Country Stuff the Album''. Hayes and Shane McAnally co-wrote the song with Luke Laird Luke ...

, a 2021 single by Walker Hayes *

Ace Attorney ''Ace Attorney'' is a series of visual novel adventure video games developed by Capcom. With storytelling fashioned after legal dramas, the first entry in the series, ''Phoenix Wright: Ace Attorney'', was released in 2001; since then, five f ...

, a series of video games developed by Capcom. *

AA Films AA Films is an Indian motion picture distribution company, owned by Anil Thadani. It mainly distributes Hindi films and Hindi-dubbed South Indian films in North India North India is a loosely defined region consisting of the northern pa ...

, an Indian film distribution company *

AA Book (disambiguation) AA Book may refer to: *''Projects Review'', or the AA Book, of the Architectural Association School of Architecture *''The Big Book'' of Alcoholics Anonymous *Books published by The Automobile Association See also

*AA (disambiguation) {{disam ...

*AA, the production code for the 1966 ''Doctor Who'' serial '' The Savages''

Brands, organizations and enterprises

Alcoholics Anonymous Alcoholics Anonymous (AA) is an international mutual aid fellowship of alcoholics dedicated to abstinence-based recovery from alcoholism through its spiritually-inclined Twelve Step program. Following its Twelve Traditions, AA is non-professi ...

, an international fellowship dedicated to helping alcoholics peer to peer in sobriety *

A. A. Arms Intratec was a firearm company based in Miami, Florida. The company's most famous product was the Intratec TEC-DC9, TEC-9. History Intratec began as Interdynamic USA, an offshoot of Swedish firearms manufacturer Interdynamic AB. As a result of ...

, a defunct firearms manufacturer *

Aerolíneas Argentinas Aerolíneas Argentinas, formally Aerolíneas Argentinas S.A., is Argentina's largest airline and the country flag carrier. The airline was created in 1949 from the merger of four companies and started operations in . A consortium led by Iberia ...

, an Argentine airline (logo used to consist of two A's) *

Air Asia Capital A Berhad, () operating as AirAsia (stylized as ''airasia'') is a Malaysian multinational low-cost airline headquartered near Kuala Lumpur, Malaysia. It is the largest airline in Malaysia by fleet size and destinations. AirAsia operate ...

, an Asian multinational low cost carrier *

Alcoa Alcoa Corporation (an acronym for Aluminum Company of America) is a Pittsburgh-based industrial corporation. It is the world's eighth-largest producer of aluminum. Alcoa conducts operations in 10 countries. Alcoa is a major producer of primary ...

, an American aluminum-producing company (stock symbol AA) *

American Airlines American Airlines is a major airlines of the United States, major US-based airline headquartered in Fort Worth, Texas, within the Dallas–Fort Worth metroplex. It is the Largest airlines in the world, largest airline in the world when measured ...

, major American full-service airline (IATA airline code, logo used to consist of two A’s) *

Anadolu Agency Anadolu Agency ( tr, Anadolu Ajansı, ; abbreviated AA) is a state-run news agency headquartered in Ankara, Turkey. History The Anadolu Agency was founded in 1920 during the Turkish War of Independence by the order of Mustafa Kemal Ataturk. As ...

, a state-run press agency in Turkey *

Audio-Animatronics Audio-Animatronics (also known as simply Animatronics, and sometimes shortened to AAs) is the registered trademark for a form of robotics animation created by Walt Disney Imagineering for shows and attractions at Disney theme parks, and subsequent ...

, used at the Disney Parks *

Academia de Artes The Academia de Artes (AA) is the Mexican Academy of Arts founded 1967/1968 by CONACULTA for the promotion of Mexican art. Seat of the institution is the Museo Nacional de San Carlos in Mexico City. The Slogan of the Acadademy is ''elevación por el ...

, Mexico *

Amalgamated Association of Iron and Steel Workers Amalgamated Association of Iron and Steel Workers (AA) was an American labor union formed in 1876 to represent iron and steel workers. It partnered with the Steel Workers Organizing Committee of the CIO, in November 1935. Both organizations di ...

, a former union in the United States *

Andecha Astur "socialist and nationalist flag of Asturias used by Andecha Astur Andecha Astur (Asturian language, Asturian for: ''Asturian Group'') is an Asturian nationalism, Asturian nationalist leftist political party of Spain. History The party was fou ...

, an Asturian nationalist party *

Architectural Association School of Architecture The Architectural Association School of Architecture in London, commonly referred to as the AA, is the oldest Independent school (United Kingdom), independent school of architecture in the UK and one of the most prestigious and competitive in t ...

, London, United Kingdom *

Astrological Association of Great Britain The Astrological Association is a British astrological organisation. The Astrological Association of Great Britain (AA) was formed in London on 21 June 1958. Its founding members, notably John Addey and Roy Firebrace Brigadier Roy Charles Whit ...

, London, United Kingdom * ''

Auswärtiges Amt , logo = DEgov-AA-Logo en.svg , logo_width = 260 px , image = Auswaertiges Amt Berlin Eingang.jpg , picture_width = 300px , image_caption = Entrance to the Foreign Office building , headquarters = Werderscher Mark ...

'', the Foreign Office of Germany *

Danish Association of Architects The Danish Association of Architects (Danish: , abbreviated to AA), is an independent professional body for architects in Denmark. History The Danish Association of Architects was founded at the initiative of L. A. Petersen on 21 November 1879 ...

(''Akademisk Arkitektforening'') *

The AA AA Limited, trading as The AA (formerly The Automobile Association), is a British motoring association. Founded in 1905, it provides vehicle insurance, driving lessons, breakdown cover, loans, motoring advice, road maps and other services. Th ...

(formerly The Automobile Association), a British motoring organization *

AA Ireland AA Ireland Ltd is an automotive services company in Ireland, founded in 1910. It provides rescue services, personal lines insurance, and travel, technical and information services. Its AA Roadwatch service supplies traffic and travel information ...

, an Irish automotive services company *

AA Motoring Trust IAM RoadSmart formerly called the Institute of Advanced Motorists (IAM) is a charity based in the United Kingdom and serving nine countries, whose objective is to improve car driving and motorcycle riding standards, and so enhance road safety, b ...

, a former British road safety charity operated by The AA that was merged to form the

IAM Motoring Trust IAM RoadSmart formerly called the Institute of Advanced Motorists (IAM) is a charity based in the United Kingdom and serving nine countries, whose objective is to improve car driving and motorcycle riding standards, and so enhance road safety, b ...

Philosophy and religion

A∴A∴ The A∴A∴ ( ) is a magical organization described in 1907 by occultist Aleister Crowley. Its members are dedicated to the advancement of humanity by perfection of the individual on every plane through a graded series of universal initiation ...

, a spiritual organization created in 1907 by Aleister Crowley *

Abhisamayalankara The "Ornament of/for Realization , abbreviated AA, is one of five Sanskrit-language Mahayana śastras which, according to Tibetan tradition, Maitreya revealed to Asaṅga in northwest India circa the 4th century AD. (Chinese tradition recogni ...

, or Abhisamaya-alaṅkāra, a Mahayana Buddhist text *

Augustinians of the Assumption The Assumptionists, officialy named the Congregation of the Augustinians of the Assumption ( la, Congregatio Augustinianorum ab Assumptione) abbreviated AA,is a Catholic clerical religious congregation of Pontifical Right for men (priests and b ...

, a congregation of Catholic religious (priests and brothers) *

Statue of A'a from Rurutu The Statue of A'a from Rurutu is a wooden sculpture of the god A'a that was made on the Pacific island of Rurutu in the Austral archipelago. In the early nineteenth century, the sculpture was given by the islanders to the London Missionary Soc ...

, a wooden fertility-god sculpture from the Pacific island of Rurutu * "

A is A In logic, the law of identity states that each thing is identical with itself. It is the first of the historical three laws of thought, along with the law of noncontradiction, and the law of excluded middle. However, few systems of logic are bui ...

", an expression of the law of identity: each thing is identical with itself

Language

* aa, Latin-script digraph used in the orthographies of Dutch, Finnish and other languages * aa, representation of letter Å in several Scandinavian languages * aa, a

romanization of Arabic The romanization of Arabic is the systematic rendering of written and spoken Arabic in the Latin script. Romanized Arabic is used for various purposes, among them transcription of names and titles, cataloging Arabic language works, language ed ...

letter alif ا * Ꜳ, an

orthographic ligature In writing and typography, a ligature occurs where two or more graphemes or letters are joined to form a single glyph. Examples are the characters æ and œ used in English and French, in which the letters 'a' and 'e' are joined for the first ...

Afar language The Afar language ( aa, Qafaraf, links=no; also known as ’Afar Af, Afaraf, Qafar af) is an Afroasiatic language belonging to the Cushitic branch. It is spoken by the Afar people inhabiting Djibouti, Eritrea and Ethiopia. Classification Afar ...

(ISO 639-1 language code aa) * Aa (Bengali), a Bengali letter

Measurements

* AA, a

bra size Bra size (also known as brassiere measurement or bust size) indicates the size characteristics of a bra. While there are a number of bra sizing systems in use around the world, the bra sizes usually consist of a number, indicating the size of the ...

* AA, a width in

shoe size A shoe size is an indication of the fitting size of a shoe for a person. There are a number of different shoe-size systems used worldwide. While all shoe sizes use a number to indicate the length of the shoe, they differ in exactly what they me ...

s * AA battery size

Nature

* ''Aa'' (plant), a genus of orchid * ''Aa'' (snail), a subgenus of snail *

ʻAʻā Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or und ...

or aa, a form of lava * A term for "river" in German hydronymy, see

Aach (toponymy) ''Aach'' (variants ''Ach'', ''Ache''; ''Aa'') is a widespread Upper German hydronym, from an Old High German ''aha'' (Proto-Germanic '' *ahwō'') "running water" (ultimately from PIE '' *hakʷā-'' "(moving) water"). The word has also been reduced ...

People

* Aa (surname), a Scandinavian surname, including a list of people with this name *

Van der Aa (surname) Van der Aa is a Dutch language, Dutch toponymic surname meaning "from the AA (disambiguation)#Rivers, Aa (river)", of which there are a few dozen in the Low Countries alon Those bearing this name include: *Abraham Jacob van der Aa (1792-1857), Dutc ...

, a Dutch surname, including a list of people with this name *

Aa (architect) Aa, possibly AaAa (ˁȝˁȝ), was an ancient Egyptian architect and construction supervisor. His title was "Overseer of Construction Workers" or "Great Overseer of Construction Workers". He lived in the time of the Middle Kingdom of Egypt (between ...

, an architect in ancient Egypt *

Anthony Armstrong (writer) George Anthony Armstrong Willis (1897–1976), known as Anthony Armstrong, was an Anglo-Canadian writer, dramatist and essayist. A humorist who contributed to ''Punch'' and ''The New Yorker'' magazines, he wrote well-plotted crime plays includ ...

(1897–1972), Anglo-Canadian writer who used the pseudonym A.A.

Places

Aa, Estonia Aa is a village in northern Estonia, on the southern coast of the Gulf of Finland in the eastern part of the Lüganuse Parish of Ida-Viru County, from Lüganuse. (retrieved 28 July 2021) Part of the village, including the Aa manor house, is ...

, a village and beach in Estonia *

Aa, Indonesia Aa is a populated place in the South Sulawesi province of Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the Indian and Pacific oceans. It consists of over 17,000 islands, in ...

, a populated place in the South Sulawesi province of Indonesia *

Ann Arbor Anne, alternatively spelled Ann, is a form of the Latin female given name Anna (name), Anna. This in turn is a representation of the Hebrew Hannah (given name), Hannah, which means 'favour' or 'grace'. Related names include Annie (given name), ...

, a city in Michigan, United States of America

Rivers

Belgium

Aa (Nete) AA, Aa, Double A, or Double-A may refer to: Arts, entertainment and media * ''America's Army'', a 2002 computer game published by the U.S. Army * '' Ancient Anguish'', a computer game in existence since 1992 * Aa!, a J-Pop musical group * Dou ...

, a river in the province of Antwerp, which joins the Nete

France

Aa (France) The Aa (; pcd, Abbe) is a river in northern France that is 93 km (58 miles) long. Originating near the village of Bourthes and emptying into the North Sea near Gravelines, the Aa is located near the north-eastern limit of the English Channel. ...

, a river in northern France

Germany

Aabach (Afte) The Aabach (also: ''Große Aa'') is a river in Germany, a left tributary of the river Afte. It rises near the village Madfeld, part of the town Brilon, in eastern North Rhine-Westphalia near the border with Hesse. From there it flows north betw ...

, formerly called the Große Aa, a river in North Rhine-Westphalia *

Aa (Möhne) Aa is a river of North Rhine-Westphalia, Germany. It is long and is a left tributary of the Möhne in Brilon Brilon (; Westphalian language, Westphalian: ''Brailen'') is a town in North Rhine-Westphalia, central Germany, that belongs to the ...

, a river in North Rhine-Westphalia * Aa (Nethe), a river in North Rhine-Westphalia *

Aa (Werre) Aa (also: ''Westfälische Aa'', "Westphalian Aa") is a river of North Rhine-Westphalia, Germany. It is a left tributary of the Werre, which it joins in Herford. It is formed by the confluence of two small streams in Bielefeld-Milse. In its upper ...

, a river in North Rhine-Westphalia *

Bocholter Aa Bocholter Aa is a river of North Rhine-Westphalia, Germany, and the Achterhoek of the Netherlands. It flows through the town Bocholt. Its last part, before joining the Oude IJssel in Ulft, is called Aa-strang in Dutch. See also *List of rivers ...

, a river in North Rhine-Westphalia *

Dreierwalder Aa Dreierwalder Aa (also: ''Ibbenbürener Aa'', ''Ledder Mühlenbach'', ''Hörsteler Aa'') is a river of North Rhine-Westphalia, Germany. It flows into the Speller Aa in Spelle. See also *List of rivers of North Rhine-Westphalia A list of rivers o ...

, a river in North Rhine-Westphalia *

Kleine Aa (Aabach) Kleine Aa (or the Little Aabach) is a river of North Rhine-Westphalia, Germany, a tributary of the Aabach. Thus it is part of the Rhine River Basin. The Kleine Aa rises in East Westphalia 7 km north of the border to Hesse, between Bad Wunn ...

, a tributary of the Aabach in North Rhine-Westphalia *

Große Aa The Große Aa is a , right, eastern tributary of the River Ems in western Lower Saxony (Germany). It begins in the ''Samtgemeinde'' Freren, near the quarter of Overwater, at the confluence of the Deeper Aa and Ahe rivers. From there is flows t ...

, a tributary of the Ems in Lower Saxony *

Große Aa (Aabach) The Aabach (also: ''Große Aa'') is a river in Germany, a left tributary of the river Afte. It rises near the village Madfeld, part of the town Brilon, in eastern North Rhine-Westphalia near the border with Hesse. From there it flows north betw ...

, a tributary of the Aabach in North Rhine-Westphalia * Münstersche Aa, a river in North Rhine-Westphalia *

Schaler Aa Schaler Aa is a river of Lower Saxony and North Rhine-Westphalia, Germany. It flows into the Große Aa south of Freren. The river springs as Weeser Aa southeast of the Ankum Heights and east of Merzen in Lower Saxony. After crossing the boundar ...

, a river in Lower Saxony and North Rhine-Westphalia *

Speller Aa Speller Aa is a river of North Rhine-Westphalia and Lower Saxony, Germany. It flows into the Große Aa near Lünne. The upper reaches of the Speller Aa have other names, from the source to the mouth Stollenbach, Mettinger Aa, Recker Aa, Hopste ...

, a river in Lower Saxony and North Rhine-Westphalia * Steinfurter Aa, a river in North Rhine-Westphalia

Netherlands

Aa (Meuse) The Aa () is a small river in the Netherlands. It rises near Nederweert in the southeastern province of Limburg, in the Peel region. It flows northwest through the province of North Brabant towards 's-Hertogenbosch, roughly along the Zuid-Wille ...

, a river in North Brabant, which joins the Dommel to form the Dieze *

Aa of Weerijs AA, Aa, Double A, or Double-A may refer to: Arts, entertainment and media * ''America's Army'', a 2002 computer game published by the U.S. Army * ''Ancient Anguish'', a computer game in existence since 1992 * Aa!, a J-Pop musical group * Doubl ...

, a river in North Brabant, which joins the Mark at Breda *

Drentsche Aa The Drentsche Aa () is a river rising in the Netherlands, Dutch province of Drenthe, flowing through Drenthe and for the last part the province of Groningen (province), Groningen. It ends in the Schipsloot near Haren, which flows into the Noord-Wi ...

, a river in Drenthe and Groningen *

Mussel Aa Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, w ...

, a river in Westerwolde, Groningen * , a river in Westerwolde, Groningen * Westerwoldsche Aa, a river near

Oudeschans Oudeschans () is a small village with a population of around 100 in the municipality of Westerwolde in the province of Groningen in the Netherlands. The 16th-century fortification is now a state protected village area with several national heri ...

, Groningen

Switzerland

Aabach (Aare) The Aare () or Aar () is a tributary of the High Rhine and the longest river that both rises and ends entirely within Switzerland. Its total length from its source to its junction with the Rhine comprises about , during which distance it descend ...

, a tributary of the Aare in canton of Aargau *

Aabach (Greifensee) The Aabach (also ''Aa'', or ''Ustermer Aa'' for disambiguation with the Mönchaltorfer Aa) is a minor river in the canton of Zürich, Switzerland. At a length of , it flows from Pfäffikersee to the Greifensee. Its valley is known as ''Aatal'' ...

, or Ustermer Aa, a river in canton of Zürich *

Aabach (Obersee) Aabach may refer to: Germany * Aabach (Afte), a tributary of the Afte, North Rhine-Westphalia * Aabach (Hessel), a small river in the Ems river system, North Rhine-Westphalia * Kleine Aa (Aabach) (also the little Aabach), a tributary of the Aaba ...

, a tributary of Obersee (Zürichsee), in canton of St. Gallen *

Aabach (Seetal) The Aabach is a small river that runs through the Switzerland, Swiss cantons of Canton of Lucerne, Lucerne and Canton of Aargau, Aargau, in the Aare catchment area. It flows from south to north through the valley called Seetal (lit.: ''Lake Valley ...

, a river in the cantons of Lucerne and Aargau, runs through Lake Hallwyl * Chli Aa (Sempachersee), a tributary of Lake Sempach in the canton of Lucerne *

Engelberger Aa Engelberger Aa (or ''Engelbergeraa'') is a river in Switzerland. It rises west of Surenenpass in the Canton of Uri, flows through the valley of Engelberg ( Obwalden) and Nidwalden. At Buochs, it empties into Lake Lucerne and is thus a tribut ...

, a river in the cantons of Obwalden and Nidwalden, tributary of Lake Lucerne *

Gross Aa (Sempachersee) __NOTOC__ Lake Sempach (German: ''Sempachersee'') is a lake in the canton of Lucerne, Switzerland. Its area is about and its maximum depth is . A island named ''Gamma Insel'' is located east of Sursee. In the 17th century the lake counted with ...

, a tributary of Lake Sempach in the canton of Lucerne *

Mönchaltorfer Aa Greifensee is a lake in the canton of Zürich in Switzerland. Geography Greifensee is located to the east of the city of Zurich, separated by the Pfannenstiel from Lake Zürich. As the second largest lake in the canton of Zurich (Lake Zu ...

, a tributary of Greifensee in canton of Zürich *

Sarner Aa (river) The Sarner Aa is a long river in the Swiss canton of Obwalden. It drains the area to the eastern side of the Brünig Pass, flowing through the Lake Lungern, Lake Sarnen and the Wichelsee, before entering Lake Lucerne near Alpnach. It goes by sev ...

, a river in Obwalden, tributary of Lake Lucerne

Latvia

Gauja The Gauja River ( et, Koiva jõgi, german: Livländische Aa) is a river in the Vidzeme region of Latvia. It is the only large river of Latvia that begins and ends its flow in Latvia. Its length is 460 km, of which 93.5 km (approxim ...

, a river in Latvia, formerly known as ''Livländische Aa'' *

Lielupe The Lielupe ( in Latvian literally: ''Large River'', lt, Lielupė, german: Kurländische Aa) is a river in central Latvia. Its length is (the length would reach if the Mēmele River were counted as part of the Lielupe). The surface area of ...

, a river in Latvia, formerly known as ''Kurländische Aa''

Science and technology

AA amyloidosis AA amyloidosis is a form of amyloidosis, a disease characterized by the abnormal deposition of fibers of insoluble protein in the extracellular space of various tissues and organs. In AA amyloidosis, the deposited protein is serum amyloid A protein ...

, a form of amyloidosis related to serum amyloid A *

Amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

, often abbreviated ''aa'' when indicating positions in a peptide sequence (e.g., aa 120–150) *

Antiandrogen Antiandrogens, also known as androgen antagonists or testosterone blockers, are a class of drugs that prevent androgens like testosterone and dihydrotestosterone (DHT) from mediating their biological effects in the body. They act by blocking the ...

, a drug which blocks the effects of androgens *

Aplastic anemia Aplastic anemia is a cancer in which the body fails to make blood cells in sufficient numbers. Blood cells are produced in the bone marrow by stem cells that reside there. Aplastic anemia causes a deficiency of all blood cell types: red blood ...

, a rare disease *

Arachidonic acid Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega-6 fatty acid 20:4(ω-6), or 20:4(5,8,11,14). It is structurally related to the saturated arachidic acid found in cupuaçu butter. Its name derives from the New Latin word ''arachi ...

, a polyunsaturated fatty acid * Advanced Architecture, original name of

Amiga Advanced Graphics Architecture Amiga Advanced Graphics Architecture (AGA) is the third-generation Amiga graphic chipset, first used in the Amiga 4000 in 1992. Before release AGA was codenamed Pandora by Commodore International. AGA was originally called AA for Advanced Archit ...

Anti-aliasing Anti-aliasing may refer to any of a number of techniques to combat the problems of aliasing in a sampled signal such as a digital image or digital audio recording. Specific topics in anti-aliasing include: * Anti-aliasing filter, a filter used be ...

, various techniques for mitigating certain signal processing artifacts *

Atlas Autocode Atlas Autocode (AA)Original scans)) is a programming language developed around 1965 at the University of Manchester. A variant of the language ALGOL, it was developed by Tony Brooker and Derrick Morris for the Atlas computer. The AA compiler was ...

, a computer programming language * AA, a proprietary digital audio format of

Audible.com Audible is an American online audiobook and podcast service that allows users to purchase and stream audiobooks and other forms of spoken word content. This content can be purchased individually or under a subscription model where the user receiv ...

Authoritative Answer The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned to ...

, in DNS, a flag for a query answer *

AA postulate In Euclidean geometry, the AA postulate states that two triangles are similar if they have two corresponding angles congruent. The AA postulate follows from the fact that the sum of the interior angles of a triangle is always equal to 180°. By ...

of Euclidean geometry *

Anti-aircraft Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...

, in military use *

Abampere The abampere (abA), also called the biot (Bi) after Jean-Baptiste Biot, is the derived electromagnetic unit of electric current in the emu-cgs system of units (electromagnetic cgs). One abampere corresponds to ten amperes in the SI system of uni ...

(aA), the CGS unit of current * Attoampere (aA), a unit of electric current equal to 10⁻¹⁸

Ampere The ampere (, ; symbol: A), often shortened to amp,SI supports only the use of symbols and deprecates the use of abbreviations for units. is the unit of electric current in the International System of Units (SI). One ampere is equal to elect ...

AA tree An AA tree in computer science is a form of balanced tree used for storing and retrieving ordered data efficiently. AA trees are named after Arne Andersson, the one who theorized them. AA trees are a variation of the red–black tree, a form of ...

, named after Arne Andersson * AA, the abbreviation for

azidoazide azide 1-Diazidocarbamoyl-5-azidotetrazole, often jokingly referred to as azidoazide azide, is a heterocyclic inorganic compound with the formula C2N14. It is an extremely sensitive explosive. Synthesis 1-Diazidocarbamoyl-5-azidotetrazole was produced ...

AppArmor AppArmor ("Application Armor") is a Linux kernel security module that allows the system administrator to restrict programs' capabilities with per-program profiles. Profiles can allow capabilities like network access, raw socket access, and the ...

Sports

Double-A (baseball) Double-A (officially Class AA) is the second-highest level of play in Minor League Baseball in the United States since 1946, below only Triple-A. There are currently 30 teams classified at the Double-A level, one for each team in Major League ...

or Class AA, a classification level in Minor League Baseball since 1912 *

American Association (1882–1891) The American Association of Base Ball Clubs (AA) was a professional baseball league that existed for 10 seasons from to . Together with the National League (NL), founded in , the AA participated in an early version of the World Series seven ti ...

, a professional baseball league in the United States from 1882 to 1891 *

American Association (1902–1997) The American Association (AA) was a Minor League Baseball league that operated primarily in the Midwestern and South Central United States from 1902 to 1962 and 1969 to 1997. It was classified as a Triple-A league, which is one grade below Maj ...

, a professional baseball league in the United States from 1902 to 1962 and 1969 to 1997 *

American Association of Professional Baseball The American Association of Professional Baseball is an independent professional baseball league founded in 2005. It operates in the central United States and Canada, mostly in cities not served by Major League Baseball teams or their minor lea ...

, a professional baseball league in the United States and Canada since 2006 *

Athletics Australia Athletics Australia is the national sporting organisation (NSO) recognised by Sport Australia for the sport of athletics in Australia. First founded in 1897, the organisation is responsible for administering a sport with over 16,000 registered ...

, national sporting organisation in Australia

Transportation

AA Highway The AA Highway is a state highway maintained by the Kentucky Transportation Cabinet (KYTC) in the U.S. state of Kentucky. The mainline route parallels the Ohio River from Interstate 275 (I-275) in Wilder to Vanceburg; it is cosigned as Kentuck ...

, a state highway in Northern Kentucky *

Ann Arbor Railroad (1895–1976) The Ann Arbor Railroad was an American railroad that operated between Toledo, Ohio, and Elberta and Frankfort, Michigan (about 294 route miles) with train ferry operations across Lake Michigan. In 1967 it reported 572 million net ton-miles of ...

, a defunct railroad in Ohio and Michigan *

Ann Arbor Railroad (1988) The Ann Arbor Railroad is a Class III Railroad that operates fifty miles of track from Toledo, Ohio, to Osmer, Michigan. The railroad is operated by Watco and is based out of Toledo. Prior to Watco, the railroad was operated by the Ann Arbor Acq ...

, a railroad operating in Ohio and Michigan * ''K'' line, a defunct line on the New York City Subway, formerly called "AA" * NZR A^A class, a locomotive class operated by the New Zealand Railways Department

Other uses

African American African Americans (also referred to as Black Americans and Afro-Americans) are an ethnic group consisting of Americans with partial or total ancestry from sub-Saharan Africa. The term "African American" generally denotes descendants of ens ...

, as a cultural identity *

Asian Aerospace Asian Aerospace (AA) is an international trade fair for the aerospace business. Currently based in Hong Kong, it was held in Singapore since 1981 until disagreements between co-organisers Reed Exhibitions and Singapore Technologies in 2006 forced ...

, an airshow in Asia *

Associate of Arts An associate degree is an undergraduate degree awarded after a course of post-secondary study lasting two to three years. It is a level of qualification above a high school diploma, GED, or matriculation, and below a bachelor's degree. The fi ...

, an academic degree *

European Union Association Agreement A European Union Association Agreement or simply Association Agreement (AA) is a treaty between the European Union (EU), its Member States and a non-EU country that creates a framework for co-operation between them. Areas frequently covered by su ...

* Postal abbreviation for United States armed forces in the Americas * Japanese internet slang for

Shift JIS art Shift_JIS art is artwork created from characters in the Shift JIS character set, a superset of the ASCII encoding standard intended for Japanese usage. Shift_JIS art has become popular on web-based bulletin boards, notably 2channel, and has e ...

* Internet slang for

ASCII Art ASCII art is a graphic design technique that uses computers for presentation and consists of pictures pieced together from the 95 printable (from a total of 128) characters defined by the ASCII Standard from 1963 and ASCII compliant chara ...