A is the first letter and a vowel in the basic modern Latin alphabet. It is similar to the Ancient Greek letter Alpha, from which it derives.- Origins :...
is the first letter of the Latin alphabet.
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A is the first letter and a vowel in the basic modern Latin alphabet. It is similar to the Ancient Greek letter Alpha, from which it derives.- Origins :...
is the first letter of the Latin alphabet.
A may also refer to:
- A battery, a vacuum tube filament battery
- Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
, also called retinol, an essential human nutrient
- Haplogroup A (mtDNA)
In human mitochondrial genetics, Haplogroup A is a human mitochondrial DNA haplogroup.-Origin:Haplogroup A is believed to have arisen in Asia some 30,000-50,000 years before present...
, a human mitochondrial DNA (mtDNA) haplogroup
- Haplogroup A (Y-DNA)
In human genetics, Haplogroup A refers to a group of y-chromosome lineages that were among the first to branch off from the root of the human y-chromosome phylogeny...
, a Y-chromosomal DNA (Y-DNA) haplogroup
- A+ and A-, human blood type
A blood type is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells . These antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system...
Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...
, nucleic acid
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
, amino acid
- Adenosine, nucleoside
- ATC code A, Alimentary tract and metabolism, a section of the Anatomical Therapeutic Chemical Classification System
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....
, an electrode
- The center of a hexagonal face of the Brillouin zone
In mathematics and solid state physics, the first Brillouin zone is a uniquely defined primitive cell in reciprocal space. The boundaries of this cell are given by planes related to points on the reciprocal lattice. It is found by the same method as for the Wigner–Seitz cell in the Bravais lattice...
of a hexagonal lattice, in physics
- The letter "A" was formerly the chemical symbol for the element argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
, which is now indicated by the symbol Ar.
- A whitish-blue class of stars in the Morgan-Keenan system, see stellar classification
In astronomy, stellar classification is a classification of stars based on their spectral characteristics. The spectral class of a star is a designated class of a star describing the ionization of its chromosphere, what atomic excitations are most prominent in the light, giving an objective measure...
- A January 1 through 15 discovery in the provisional designation of a comet (for example, C/1760 A1
The Great Comet of 1760 was first seen on 7 January 1760 by Abbe Chevalier at Lisbon. Charles Messier also spotted the comet on 8 January 1760 in Paris, by the sword of Orion. The comet was his third discovery and the comet was the 51st to have a calculated orbit...
- The semi-major axis
The major axis of an ellipse is its longest diameter, a line that runs through the centre and both foci, its ends being at the widest points of the shape...
of an orbit
Abbreviations for physical and chemical quantities and units
In physics, acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity. ...
- the unique, or one of the, reciprocal lattice vector(s) (a*)
- attenuation coefficient
The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter. A large attenuation coefficient means that the beam is quickly "attenuated" as it passes through the medium, and a small...
- activity (chemistry)
In chemical thermodynamics, activity is a measure of the “effective concentration” of a species in a mixture, meaning that the species' chemical potential depends on the activity of a real solution in the same way that it would depend on concentration for an ideal solution.By convention, activity...
- specific surface area
Specific surface area is a material property of solids which measures the total surface area per unit of mass, solid or bulk volume, or cross-sectional area...
- thermal diffusivity
In heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure. It has the SI unit of m²/s...
- unit cell length (a)
- Bohr radius
The Bohr radius is a physical constant, approximately equal to the most probable distance between the proton and electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom...
Adsorption is the adhesion of atoms, ions, biomolecules or molecules of gas, liquid, or dissolved solids to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. It differs from absorption, in which a fluid permeates or is dissolved by a liquid or solid...
- 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
The van der Waals equation is an equation of state for a fluid composed of particles that have a non-zero volume and a pairwise attractive inter-particle force It was derived by Johannes Diderik van der Waals in 1873, who received the Nobel prize in 1910 for "his work on the equation of state for...
- magnetic vector potential (A)
- absorbance (A)
Area is a quantity that expresses the extent of a two-dimensional surface or shape in the plane. Area can be understood as the amount of material with a given thickness that would be necessary to fashion a model of the shape, or the amount of paint necessary to cover the surface with a single coat...
- A value
thumb|400px|right| The A-value for a [[methyl]] group is 1.74 as derived from the [[chemical equilibrium]] above. This means it costs 1.74 [[kcal/mol]] of energy to have a methyl group in the axial position compared to the equatorial position....
(A), a measure of substituent effects on the stereochemistry of cyclohexane
- Helmholtz free energy
In thermodynamics, the Helmholtz free energy is a thermodynamic potential that measures the “useful” work obtainable from a closed thermodynamic system at a constant temperature and volume...
- mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...
- pre-exponential factor
In chemical kinetics, the preexponential factor or A factor is the pre-exponential constant in the Arrhenius equation, an empirical relationship between temperature and rate coefficient...
- rotational constant (A)
- Hall coefficient (AH)
- relative atomic mass (Ar)
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
(A), the SI base unit of electric current
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....
(Å), a unit of length equal to 1 metres
- chemical affinity
In chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilar chemical species are capable of forming chemical compounds...
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
- Hamaker constant
The Hamaker constant A can be defined for a Van der Waals body-body interaction:A=\pi^2\times C \times \rho_1 \times \rho_2where \rho_1 and \rho_2 are the number of atoms per unit volume in two interacting bodies and C is the coefficient in the particle-particle pair interaction.The Hamaker...
- hyperfine coupling constant (a or A)
- Richardson's constant (A)
Mathematics and logic
- A numerical digit
A digit is a symbol used in combinations to represent numbers in positional numeral systems. The name "digit" comes from the fact that the 10 digits of the hands correspond to the 10 symbols of the common base 10 number system, i.e...
meaning ten in hexadecimal and other positional numeral systems with a radix of 11 or greater
- Sometimes in blackboard bold
Blackboard bold is a typeface style that is often used for certain symbols in mathematical texts, in which certain lines of the symbol are doubled. The symbols usually denote number sets...
represents the algebraic numbers ( (U+1D538 in Unicode)
- Universal quantifier in symbolic logic (symbol ∀ or (an inverted letter A)
- Mills' constant is represented by the symbol A
- Glaisher–Kinkelin constant is also often represented by the symbol A
- A*, a pathfinding algorithm
- A-0 System, early computer compiler
- A+ (programming language)
A+ is an array programming language descendent from the programming language A, which in turn was created to replace APL in 1988. Arthur Whitney developed the "A" portion of A+, while other developers at Morgan Stanley extended it, adding a graphical user interface and other language features...
- A Sharp (Axiom)
A# is an object-oriented functional programming language distributed as a separable component of Version 2 of the Axiom computer algebra system. A# types and functions are first-class values and can be used freely in conjunction with an extensive library of data structures and other mathematical...
, properly known as "A#"
- BASIC A+
BASIC A+ was developed by Optimized Systems Software of Cupertino, California, USA, to provide the Atari 8-bit family with an extended BASIC compatible with, but faster than, the simpler ROM-based Atari BASIC....
- , the HTML element for an anchor tag
- A Sharp (.NET)
A# is a port of the Ada programming language to the Microsoft .NET platform. A# is freely distributed by the Department of Computer Science at the United States Air Force Academy as a service to the Ada community under the terms of the GNU General Public License.AdaCore has taken over this...
(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
Web Content Accessibility Guidelines are part of a series of Web accessibility guidelines published by the W3C's Web Accessibility Initiative. They consist of a set of guidelines for making content accessible, primarily for disabled users, but also for all user agents, including highly limited...
- A (musical note)
La or A is the sixth note of the solfège. "A" is generally used as a standard for tuning. When the orchestra tunes, the oboe plays an "A" and the rest of the instruments tune to match that pitch. Every string instrument in the orchestra has an A string, from which each player can tune the rest of...
, the sixth solfège note
- A (band)
A are a British alternative rock band from Suffolk, England, that formed in 1993. They have released four albums, and two live mini-albums.In 2002, the band enjoyed a brief period of commercial success, in which "Nothing", the first single from Hi-Fi Serious , charted at #9 on the UK singles chart...
, a British rock band
- A (Cass McCombs album)
A is the debut album by Cass McCombs and was released on May 20, 2003 on Monitor Records.-Track listing: # "I Went to the Hospital" – 5:14# "Bobby, King of Boys Town" – 3:47# "What Isn't Nature" – 4:48# "Aids in Africa" – 5:42...
- A (Jethro Tull album)
- "A" (song)
"A" is Ayumi Hamasaki's tenth single, released on August 11, 1999. Hamasaki's best-selling single as well Japan's 57th best-selling single of all time, "A," is unique among Hamasaki's singles, as it is her only single with quadruple A-sides...
, a song by Ayumi Hamasaki
- "A", song by Barenaked Ladies from Maybe You Should Drive
- Singles :* "Jane"** Released: 1994** Formats: CD, cassette* "Alternative Girlfriend"** Released: 1995** Formats: CD- Charts :Album...
- "A", song by Cartel from Chroma
-Credits:* Nic Hudson – guitar* Julia Kugel – backing vocals* Kenneth Mount – programming* Zack Odom – strings* Joseph Pepper – guitar* Will Pugh – vocals, guitar, piano, programming* Ryan Roberts – bass* Kevin Sanders – drums* David Webers – trumpet...
- "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 gramophone record, commonly known as a phonograph record , vinyl record , or colloquially, a record, is an analog sound storage medium consisting of a flat disc with an inscribed, modulated spiral groove...
- "A", major poem by 20th century author Louis Zukofsky
Louis Zukofsky was an American poet. He was one of the founders and the primary theorist of the Objectivist group of poets and thus an important influence on subsequent generations of poets in America and abroad.-Life:...
- a, A Novel
a, A Novel is a 1968 book by the American artist Andy Warhol published by Grove Press. It is a nearly word-for-word transcription of tapes recorded by Warhol and Ondine over a two-year period in 1966-1968.-The Novel:...
, by 20th century artist Andy Warhol
- A, the name of the Fourth Raikage, the leader of Kumogakure in the Naruto
is an ongoing Japanese manga series written and illustrated by Masashi Kishimoto. The plot tells the story of Naruto Uzumaki, an adolescent ninja who constantly searches for recognition and aspires to become the Hokage, the ninja in his village who is acknowledged as the leader and the strongest of...
- 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
- A, a rating in India's Central Board of Film Certification
The Central Board of Film Certification is a Government of India regulatory body and censorship board of India controlled by Ministry of Information and Broadcasting. It reviews, rates and censors motion pictures, television shows, television ads, and promotional material...
- A certificate, a film rating used by the Canadian motion picture rating system
Motion picture ratings in Canada are mostly a provincial responsibility, and each province has its own legislation regarding exhibition and admission...
- A, a British Board of Film Classification rating used from 1912–1982, see History of British film certificates
-Overview:The UK's film ratings are decided by the British Board of Film Classification and have been since 1912. Previously, there were no agreed rating standards, and local councils imposed their own - often differing - conditions or restrictions...
- A!, a common internet abbreviation for Animaniacs
Steven Spielberg Presents Animaniacs, usually referred to as simply Animaniacs, is an American animated series, distributed by Warner Bros. Television and produced by Amblin Entertainment and Warner Bros. Animation. The cartoon was the second animated series produced by the collaboration of Steven...
- A (TV system), a Canadian television system formerly known as A-Channel
- A and an, the indefinite article in English
- A (kana)
あ in hiragana or ア in katakana is one of the Japanese kana that each represent one mora. あ is based on the sōsho style of kanji 安, and ア is from the radical of kanji 阿. In the modern Japanese system of alphabetical order, it occupies the first position of the alphabet, before い. Additionally, it...
, the Japanese kana あ and ア which may be used to represent Asia
- A (Cyrillic)
A is a letter of the Cyrillic alphabet.It commonly represents an open front unrounded vowel , like the pronunciation of ⟨a⟩ in "father".The Cyrillic letter A is romanized using the Latin letter A.-History:...
, the first letter of the Cyrillic alphabet, the IPA representation of the open front unrounded vowel, the IPA representation of the open back unrounded vowel
- A (New York City Subway service)
The A Eighth Avenue Express is a rapid transit service of the New York City Subway. Its route bullet is colored blue on route signs, station signs, and the official subway map since it runs on the IND Eighth Avenue Line in Manhattan....
, also known as the "A Eighth Avenue Express"
- A (S-train)
A is a service on the S-train network in Copenhagen. It is one of the base services on the network, running every 20 minutes from about 5:00 to 0:30 every day, and every 10 minutes from about 6:15 to 19:00. It runs between Hundige and Farum, serving all stations on the inner part of the Køge radial...
a service on the S-train network in Copenhagen
- Alton Railroad
The Alton Railroad was the final name of a railroad linking Chicago to Alton, Illinois, St. Louis, Missouri, and Kansas City, Missouri. Its predecessor, the Chicago and Alton Railroad , was purchased by the Baltimore and Ohio Railroad in 1931 and was controlled until 1942 when the Alton was...
- Line A (Prague Metro)
Line A is a line of the Prague Metro, serving the Czech Republic capital. Chronologically the second line in the system, it was first opened in 1978 and has expanded mostly during the 1980s...
- A (yacht), an 118-meter megayacht owned by Andrey Melnichenko, a Kaiserliche Marine tanker
An A-frame is a basic structure designed to bear a load in a lightweight economical manner. The simplest form of an A-frame is two similarly sized beams, arranged in a 45-degree or greater angle, attached at the top...
, a type of structure
- A, the alternate name for Brfxxccxxmnpcccclllmmnprxvclmnckssqlbb11116, a Swedish child born in 1991
- Agilent Technologies
Agilent Technologies , or Agilent, is a company that designs and manufactures electronic and bio-analytical measurement instruments and equipment for measurement and evaluation...
, with U.S. ticker symbol A
- Anarchist symbolism
While anarchists have historically largely denied the importance of symbols to political movement, they have embraced certain symbols for their cause, including most prominently the circle-A and the black flag...
, an A within a circle
- An ace in a deck of playing card
A playing card is a piece of specially prepared heavy paper, thin cardboard, plastic-coated paper, cotton-paper blend, or thin plastic, marked with distinguishing motifs and used as one of a set for playing card games...
- Alpha, (sometimes A) in Christian theology
- Divisions of Christian theology :There are many methods of categorizing different approaches to Christian theology. For a historical analysis, see the main article on the History of Christian theology.- Sub-disciplines :...
is a metaphor for the beginning/creation of time and matter
- A series of paper sizes defined by ISO 216
ISO 216 specifies international standard paper sizes used in most countries in the world today. It defines the "A" and "B" series of paper sizes, including A4, the most commonly available size...
, e.g. A4, A5 sizes
- A (grade), an academic grade
- Sentinel Peak (Arizona)
Sentinel Peak, more commonly known as "A" Mountain, is a prominent ridgein the Tucson Mountains west of Tucson, Arizona.Sentinel Peak rises 2,897 feet into the air to the west of the Santa Cruz River. The underground ridge of rock, running to the east, once forced groundwater to the surface...
, 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
The Out Campaign is a public awareness initiative for freethought and atheism. It was initiated by Dr. R. Elisabeth Cornwell, Executive Director of the Richard Dawkins Foundation for Reason and Science, and is endorsed by Richard Dawkins, who is a prominent atheist...
a public awareness initiated by Elizabeth Cornwell and Richard Dawkins
- Single A, or Class A, a classification of Minor league baseball
Minor league baseball is a hierarchy of professional baseball leagues in the Americas that compete at levels below Major League Baseball and provide opportunities for player development. All of the minor leagues are operated as independent businesses...
- Å (disambiguation)
Å is a letter used in several Scandinavian, High German, and Sami languages.Å may also refer to:-Places:Å means stream or river in Scandinavian languages...
- A band (disambiguation)
- A class (disambiguation)
- Class A (disambiguation)
- Alpha (disambiguation)
- Aleph (disambiguation)