A (disambiguation) in Encyclopedia

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 10¹⁸
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 (A_H)
relative atomic mass (A_r)
ampere (A), the SI base unit of electric current
ngstr m ( ), a unit of length equal to 1 metres
chemical affinity (A)
gain (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 (\mathbb{A} (U+1D538 in Unicode)
Universal quantifier in symbolic logic (symbol or \forall (an inverted letter A)
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 Sharp (Axiom), properly known as "A#"
BASIC A+
, the HTML element for an anchor tag
A Sharp (.NET) (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 arts

Music

A (musical note), the sixth solf ge note
A (band), a British rock band
A (Cass McCombs album)
A (Jethro Tull album)
"A" (song), a song 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 single by Rainbow

Literature

"A", major poem by 20th century author Louis Zukofsky
a, A Novel, by 20th 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

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

Geography

"The A", a nickname for Atlanta, Georgia

Linguistics

A and an, the indefinite article in English
A (or a), the first letter of the Latin alphabet
A (Cyrillic) (A or ), the first letter of the Cyrillic alphabet
Alpha ( or ), the first letter of the Greek alphabet
A (kana) (or a), the romanized name of the Hiragana syllable letter and of the Katakana syllable letter used in Japanese, which may also be used to represent Asia
, the IPA representation of the open front unrounded vowel
, the IPA representation of the open back unrounded vowel

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)

Ships

A (yacht), an 118-meter megayacht owned by Andrey Melnichenko
, 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 (disambiguation)

Contents

Science

Astronomy

Abbreviations for physical and chemical quantities and units

Mathematics and logic

Computing

The arts

Music

Literature

Film

Film ratings

Television

Geography

Linguistics

Transport

Ships

Other

See also