A (disambiguation)
Appearance
Look up A in Wiktionary, the free dictionary.
A is the first letter of the Latin alphabet.
A may also refer to:
Science
- A battery, a vacuum tube filament battery
- 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
- A+ and A-, human blood types
- Adenine, nucleic acid
- Alanine, amino acid
- Adenosine, nucleoside
- ATC code A, Alimentary tract and metabolism, a section of the Anatomical Therapeutic Chemical Classification System
- Anode, an electrode
- The center of a hexagonal face of the Brillouin zone of a hexagonal lattice, in physics
- The letter "A" was formerly the chemical symbol for the element argon, which is now indicated by the symbol Ar.
Astronomy
- A whitish-blue class of stars in the Morgan–Keenan system, see stellar classification
- A January 1 through 15 discovery in the provisional designation of a comet (for example, C/1760 A1)
- The semi-major axis of an orbit
Abbreviations for physical and chemical quantities and units
- acceleration (a)
- the unique, or one of the, reciprocal lattice vector(s) (a*)
- attenuation coefficient (a)
- activity (chemistry) (a)
- specific surface area (a)
- thermal diffusivity (a)
- unit cell length (a)
- Bohr radius (a0)
- Adsorption (a)
- annum (a), for year
- are (a), a unit of area equal to 100 square metres (redirects to hectare)
- atto- (a), the SI prefix meaning 10−18
- a', a measure for the attraction between particles in the Van der Waals equation
- magnetic vector potential (A)
- absorbance (A)
- area (A)
- A value (A), a measure of substituent effects on the stereochemistry of cyclohexane
- Helmholtz free energy (A)
- mass number (A)
- pre-exponential factor (A)
- rotational constant (A)
- Hall coefficient (AH)
- relative atomic mass (Ar)
- ampere (A), the SI base unit of electric current
- ångström (Å), a unit of length equal to 1×10−10 metres
- chemical affinity (A)
- gain (electronics) (A)
- Hamaker constant (A)
- hyperfine coupling constant (a or A)
- Richardson's constant (A)
Mathematics and logic
- A numerical digit meaning ten in hexadecimal and other positional numeral systems with a radix of 11 or greater
- Sometimes in blackboard bold represents the algebraic numbers () (U+1D538 in Unicode)
- Universal quantifier in symbolic logic (symbol ∀ or , an inverted letter A)
- Universal affirmative, one of the four types of categorical proposition in logic
- Mills' constant is represented by the symbol A
- Glaisher–Kinkelin constant is also often represented by the symbol A
Computing
- A*, a pathfinding algorithm
- A-0 System, early computer compiler
- A+ (programming language)
- A♯, the object-oriented functional programming language distributed as a separable component of Version 2 of the Axiom computer algebra system
/a/
, the anime and manga section on 4chan- BASIC A+
<a></a>
, the HTML element for an anchor tag- a, equivalent (qname) to the RDF Schema Property rdf:type
- A# (a port of Ada to the Microsoft .NET Platform)
- The most basic of the three levels of web site accessibility measured by Web Content Accessibility Guidelines
- The address record type of DNS defined in RFC 1035
The arts
Music
- A (musical note), the sixth solfège note
- A major, a scale
- A minor, a scale
- A major chord, Chord names and symbols (popular music)
- A (band), a British rock band
- A (Agnetha Fältskog album), 2013
- A (Cass McCombs album), 2003
- A (Jimmy Raney album), 1957
- A (Jethro Tull album), 1980
- A, a Denki Groove album (read as "Ace")
- "A" (EP), a 1999 EP by Ayumi Hamasaki
- "A", song by 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
- A or Side A, the top or first side of a gramophone record
- A (Rainbow song), a 2010 single by Rainbow
Literature
- "A", major poem by twentieth century author Louis Zukofsky
- 'A', pseudonym of Matthew Arnold
- 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, the main antagonist in the Pretty Little Liars series
- A (for "adultery"), the titular letter in the novel The Scarlet Letter
- A, pseudonym of Alexander Pope
- Dr. A, pseudonym of Isaac Asimov
Film
- A (1965 film), a short film animated by Jan Lenica
- A (1998 Indian film), a Kannada 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
- 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 1912–1982, see History of British film certificates
Television
- A!, a common internet abbreviation for Animaniacs
- CTV Two, 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
Geography
- Austria, on the vehicle registration plates of the European Union
- "The A", a nickname for Atlanta, Georgia
Linguistics
- A and an, the indefinite article in English
- A, the agent-like argument of canonical transitive verb
- A (or a), the first letter of the Latin alphabet
- A (Cyrillic) (A or а), the first letter of the Cyrillic alphabet
- Alpha (Α or α), the first letter of the Greek 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
- 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
Transport
- 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)
- Ford Model A, a name used by two separate cars produced by the Ford Motor Company:
- NZR A class (disambiguation) two New Zealand steam locomitive classes
Ships
- 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
- A-Frame, a type of structure
- A, the alternate name for Brfxxccxxmnpcccclllmmnprxvclmnckssqlbb11116, a Swedish child born in 1991
- Agilent Technologies, with U.S. ticker symbol A
- Anarchist symbolism, an A within a circle
- An ace in a deck of playing cards
- Alpha, (sometimes A) in Christian theology is a metaphor for the beginning/creation of time and matter
- A series of paper sizes defined by ISO 216, e.g. A4, A5 sizes
- A (grade), an academic grade
- Sentinel Peak (Arizona), more commonly known as "A" Mountain for the man-made rock formation in the shape of the letter
- Scarlet A, symbol for atheism adopted by the Out Campaign, a public awareness initiated by Elizabeth Cornwell and Richard Dawkins
- A, the Dominical letter of a common year starting on Sunday
See also
- Single-A, or Class A, a classification of minor league baseball
- Å (disambiguation)
- A band (disambiguation)
- A class (disambiguation)
- Class A (disambiguation)
- A1 (disambiguation)
- Alpha (disambiguation)
- Aleph (disambiguation)
- AA (disambiguation)
- AAAA (disambiguation)
- AAA (disambiguation)
- Type A (disambiguation)
- Model A (disambiguation)
- A-Type (disambiguation)