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A es la primera letra del alfabeto latino e inglés.

A también puede referirse a:

Ciencia y tecnología [ editar ]

Cantidades y unidades [ editar ]

  • a ' , una medida de la atracción entre partículas en la ecuación de Van der Waals
  • Un valor ( A ), una medida de los efectos de los sustituyentes en la estereoquímica del ciclohexano.
  • Absorbancia ( A )
  • Aceleración ( a )
  • Actividad (química) ( a )
  • Adsorción (a)
  • Annum (a), por año
  • son (a), una unidad de área igual a 100 metros cuadrados (redirecciona a hectárea )
  • atto- (a), el prefijo SI que significa 10 −18
  • Amperio (A), la unidad base SI de corriente eléctrica
  • ångström (Å), una unidad de longitud igual a 1 × 10 −10 metros
  • Área ( A )
  • Coeficiente de atenuación ( a )
  • Radio de Bohr ( a 0 )
  • Afinidad química ( A )
  • Ganancia (electrónica) ( A )
  • Coeficiente Hall ( A H )
  • Constante de Hamaker ( A )
  • Energía libre de Helmholtz ( A )
  • Constante de acoplamiento hiperfina ( a o A )
  • Potencial de vector magnético ( A )
  • Número de masa ( A )
  • Factor preexponencial ( A )
  • El vector o los vectores reticulares recíprocos o únicos ( a * )
  • Masa atómica relativa ( A r )
  • Constante de Richardson ( A )
  • Constante rotacional ( A )
  • Superficie específica ( a )
  • Difusividad térmica ( a )
  • Longitud de celda unitaria ( a )

Astronomía [ editar ]

  • Una clase de estrellas de color azul blanquecino en el sistema Morgan-Keenan; ver clasificación estelar
  • Parte de la designación provisional de un cometa (p. Ej., C / 1760 A1), que indica un descubrimiento del 1 al 15 de enero
  • The semi-major axis of an orbit

Biology[edit]

  • A+ and A−, human blood types
  • Vitamin A, also called retinol, an essential human nutrient
  • Haplogroup A (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup
  • Haplogroup A (Y-DNA), a Y-chromosomal DNA (Y-DNA) haplogroup
  • Adenine, a nucleic acid
  • Adenosine, a nucleoside
  • Alanine, an amino acid
  • ATC code A, Alimentary tract and metabolism, a section of the Anatomical Therapeutic Chemical Classification System

Computing[edit]

Programming languages[edit]

  • A+ (programming language)
  • A ♯ , un lenguaje de programación funcional orientado a objetos
  • Un Sharp (.NET) (también escrito "A #"), un puerto de Ada a la plataforma Microsoft .NET
  • BÁSICO A +

Otros usos en informática [ editar ]

  • Un * algoritmo de búsqueda , un algoritmo de búsqueda de caminos
  • A-0 System , uno de los primeros compiladores informáticos
  • <a></a>, el elemento HTML de una etiqueta de anclaje
  • a, equivalente (qname) a la propiedad de esquema RDF rdf: type
  • Un nivel de accesibilidad web definido por las Pautas de accesibilidad al contenido web.
  • El tipo de registro de direcciones de DNS, definido en RFC 1035

Matemáticas y lógica [ editar ]

  • Un dígito numérico que significa diez en hexadecimal y otros sistemas numéricos posicionales con una base de 11 o más
  • A veces, en negrita representa los números algebraicos ( ) (U + 1D538 en Unicode)
  • Cuantificador universal en lógica simbólica (símbolo ∀ o , una letra A invertida)
  • Universal afirmativo, uno de los cuatro tipos de proposiciones categóricas en lógica
  • La constante de Mills está representada por el símbolo A
  • La constante Glaisher-Kinkelin también se representa a menudo con el símbolo A

Otros usos en ciencia y tecnología [ editar ]

  • A battery, a vacuum tube filament type battery
  • A battery (size), a standard battery size
  • Anode, an electrode
  • Argon, symbol formerly A, now Ar
  • The center of a hexagonal face of the Brillouin zone of a hexagonal lattice, in physics

Arts and media[edit]

Books[edit]

  • "A", a major poem by twentieth century author Louis Zukofsky
  • a, A Novel, by twentieth century artist Andy Warhol
  • A, the name of the Fourth Raikage, the leader of Kumogakure in the Naruto manga series
  • A (Pretty Little Liars), the main antagonist in the Pretty Little Liars book and TV series
  • A (for "adultery"), the titular letter in the novel The Scarlet Letter
  • "A" Is for Alibi, the first novel in Sue Grafton's "Alphabet mystery" series, published in 1982
  • Matthew Arnold, who used the pseudonym "A"
  • Isaac Asimov, who used the pseudonym "Dr. A"
  • Alexander Pope, who used the pseudonym "A"

Film and TV[edit]

Films[edit]

  • A (1965 film), a short film animated by Jan Lenica
  • A (1998 Kannada film), an Indian movie directed by Upendra
  • A (1998 Japanese film), a documentary film about a Buddhist sect called "A"
  • A (2002 film), a British documentary film

Film ratings[edit]

  • A, a rating in India's Central Board of Film Certification
  • A certificate, a film rating used by the Canadian motion picture rating system
  • A, a British Board of Film Classification rating used from 1912 to 1982, see History of British film certificates

Television[edit]

  • CTV 2, a Canadian television system formerly known as A-Channel and A
  • A, the main antagonist and unknown character of the show Pretty Little Liars
  • "A" (The Walking Dead), an episode of the television series The Walking Dead
  • A, code name of Ange, the main protagonist of the anime show Princess Principal
  • The A logo for the Spanish network Antena 3.
  • A, the production code for the 1963 Doctor Who serial An Unearthly Child

Music[edit]

  • A (musical note), the sixth solfège note
  • A major, a scale
  • A minor, a scale
  • A major chord; see Chord names and symbols (popular music)

Performers[edit]

  • A (band), a British alternative rock band

Albums[edit]

  • A (Agnetha Fältskog album), 2013
  • A (Cass McCombs album), 2003
  • A (Jimmy Raney album), 1957
  • A (Jethro Tull album), 1980
  • A (Usher and Zaytoven album), 2018
  • A, a Denki Groove album (read as "Ace")
  • A (Ayumi Hamasaki EP), a 1999 EP by Ayumi Hamasaki
  • A (Big Bang single album), a 2015 single by the Korean band Big Bang
  • A!, Alexa Feser 2019
  • A' (album), an album by Afrirampo

Songs[edit]

  • A or Side A, the top or first side of a gramophone record
  • "A" (Rainbow song), a 2010 single by Rainbow
  • "A", song by Got7 from Got Love (2014)
  • "A", song by the band Barenaked Ladies from Maybe You Should Drive
  • "A", song by Cartel from Chroma
  • "A", a song in the Dance Dance Revolution video game series, by DJ Amuro

Other media[edit]

  • /a/, the anime and manga section on 4chan
  • A, a Japanese video game rating in the Computer Entertainment Rating Organization suitable for all ages.

Geography[edit]

  • Austria, on the vehicle registration plates of the European Union
  • "The A", a nickname for the U.S. city of Atlanta, Georgia

Linguistics[edit]

Letters[edit]

  • A (or a), the first letter of the Latin alphabet
  • A (Bengali), the romanized name of the Bengali letter অ
  • A (cuneiform), the romanized name of a cuneiform sign
  • A (Cyrillic) (A or а), the first letter of the Cyrillic alphabet
  • A (kana) (or a), the romanized name of the Hiragana syllable letter あ and of the Katakana syllable letter ア used in Japanese, which may also be used to represent Asia
  • Alpha (Α or α), the first letter of the Greek alphabet

Other uses in linguistics[edit]

  • A and an, the indefinite article in English
  • A, a glossing abbreviation for agent-like argument of canonical transitive verb
  • a, the IPA representation of the open front unrounded vowel
  • ɑ, the IPA representation of the open back unrounded vowel
  • a., an abbreviation of ante (Latin for "before") used in etymologies

People[edit]

  • A Martinez, an American actor and singer
  • Matthew Arnold, who used the pseudonym "A"
  • Isaac Asimov, who used the pseudonym "Dr. A"
  • Alexander Pope, who used the pseudonym "A"
  • Brfxxccxxmnpcccclllmmnprxvclmnckssqlbb11116, a Swedish child born in 1991, alternately called "A"

Philosophy and religion[edit]

  • A, the Dominical letter of a common year starting on Sunday
  • Scarlet A, symbol for atheism adopted by the Out Campaign, a public awareness initiated by Elizabeth Cornwell and Richard Dawkins
  • Alpha, (sometimes A) in Christian theology, a metaphor for the beginning/creation of time and matter
  • An anarchist symbol, an A within a circle

Transport[edit]

Automobile[edit]

  • Ford Model A, a name used by two separate cars produced by the Ford Motor Company:
    • Ford Model A (1903–04)
    • Ford Model A (1927–31)
  • Geometry A, an electric mid-size sedan by Geely Auto

Rail[edit]

  • A (New York City Subway service), also known as the "A Eighth Avenue Express"
  • A (S-train) a service on the S-train network in Copenhagen
  • Alton Railroad (reporting mark)
  • Line A (Prague Metro)
  • NZR A class (disambiguation) two New Zealand steam locomotive classes

Ships[edit]

  • A (motor yacht) (M/Y A), a 119m yacht owned by Andrey Melnichenko
  • A (sailing yacht) (S/Y A), a 143m yacht owned by Andrey Melnichenko
  • SMS A, a Kaiserliche Marine tanker

Other uses[edit]

  • A (grade), an academic grade
  • A series of paper sizes defined by ISO 216, e.g. A4, A5 sizes
  • A-Frame, a type of structure
  • Ace, a playing card
  • Agilent Technologies, with U.S. ticker symbol A
  • Sentinel Peak (Arizona), more commonly known as "A" Mountain for the man-made rock formation in the shape of the letter
  • Alfa, the military time zone code for UTC+01:00

See also[edit]

  • Å (disambiguation)
  • ⓐ and Ⓐ, see Enclosed Alphanumerics
  • Class A (disambiguation)
  • Model A (disambiguation)
  • Circled-a (disambiguation)
  • Single-A, or Class A, a classification of minor league baseball
  • A band (disambiguation)
  • A class (disambiguation)
  • A type (disambiguation)
  • Aleph (disambiguation)
  • Alpha (disambiguation)
  • A1 (disambiguation)
  • AA (disambiguation)
  • AAA (disambiguation)
  • AAAA (disambiguation)