A (disambiguation)

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Look up A in Wiktionary, the free dictionary.

A is the first letter of the Latin alphabet. It can also refer to the following:

In the sciences:

A whitish-blue class of stars in the Morgan-Keenan system in astronomy.
A January 1 through 15 discovery, in the provisional designation of a comet (for example, C/1760 A1, the Great Comet of 1760) or asteroid (for example, (4099) 1988 AB₅).
As a comet designation prefix, indicates an object that was at first mistakenly identified as a comet, but is actually a minor planet (for example, A/2005 JM₃).
The semi-major axis of an orbit.
The symbol for the nitrogenous nucleic acid adenine, alanine and adenosine in biochemistry.
A battery, a standard size of battery.
The anode, a component of a vacuum tube.
Haplogroup A (mtDNA), a human mitochondrial DNA (mtDNA) haplogroup.
Haplogroup A (Y-DNA), a Y-chromosomal DNA (Y-DNA) haplogroup.
A human blood type, also A+ and A-.
Vitamin A (also called retinol), an essential human nutrient.
The center of a hexagonal face of the Brillouin zone of a hexagonal lattice, in physics.

Abbreviations for physical and chemical quantities and units:

acceleration (a, upper-case for an initial/constant accleration value; lower case for an instantaneous acceleration variable)
absorption coefficient (a)
activity (a)
hyperfine coupling constant (a)
specific surface area (a)
thermal diffusivity (a)
the unique, or one of the, unit cell length(a)
one of the van der Waals coefficients (a)
Bohr radius (a₀)
adsorbed
are, the deprecated symbol for the unit of surface area equal to 100 square metres
atto, the SI prefix meaning 10⁻¹⁸
year, from the Latin annum, especially in geology, archeology and astronomy; as prefixed with Mega (Ma) or Giga (Ga) to indicate periods of time.
magnetic vector potential (A)
absorbance (A)
absorption intensity (A)
affinity of reaction (A)
area (A)
Einstein transition probability (A)
Helmholtz energy, A
hyperfine coupling constant (A)
mass number (A)
nucleon number (A)
pre-exponential factor (A)
radioactive activity (A)
rotational constant (A)
spin-orbit coupling constant (A)
van der Waals-Hamaker constant (A)
Hall coefficient (A_H)
relative atomic mass (A_r)
ampere (A) , the SI base unit of electric current

In mathematics:

The area of geometric figures.
A 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 (<math>\mathbb{A}</math> (U+1D538 in Unicode).

In logic:

A symbol for the universal affirmative proposition in the general form "all x is y."
The universal quantifier in symbolic logic (symbol ∀ or <math>\forall</math> (an inverted letter A).

In computing:

As a programming language, A may refer to:
- A-0 programming language
- A+ programming language
- A Sharp (Axiom), properly known as "A#", an object-oriented functional programming language
- ARITH-MATIC, an extension of the A-2 programming language
- BASIC A+, a programming language
<a> is the HTML element for an anchor tag.
In the Mac OS, Command-A (for All), and in Windows, Ctrl-A, and selects all the text in the document, or all the pixels of an image.
A sometimes represents the set of all alphabetic characters within string patterns.
A: is the conventional address of the first floppy disk drive in CP/M-based operating systems such as DOS.
A is a security division ("Verified Protection") in the TCSEC.

The arts

In fiction, the letter worn by Hester Prynne marking her as an adulteress in the Nathaniel Hawthorne novel The Scarlet Letter was an A.
In film:
- A is an Italian film made in 1969.
- "A" is a Kannada movie directed by Upendra.
- A (Rating), in the CBFC system.
- In India, A is a movie rating, given to those intended to be seen only by adults.
In music:
- A (album), an album by progressive rock band Jethro Tull
- A (Cass McCombs album), an album by Cass McCombs
- A (band), a British alternative rock band.
- A Band, an experimental group.
- "A" (song), Ayumi Hamasaki's 10th single
- "A", a song by the band Cartel
- A (musical note), the sixth musical note.
- A (song), a song by the band Barenaked Ladies.
- A, or "side A," refers to the top or first side of a vinyl record.
In poetry, A is the major work of influential twentieth century author Louis Zukofsky.

Languages

A, an, the indefinite article in English.
In French,
- a is the Third person singular conjugation, Present tense of the verb avoir: «il a»="he has".
- à is a conjunction meaning either "with", "at", or "to": «à la carte», «à moi»; although «au» is used in place of «à le» (for masculine singular nouns) and «aux» is used in place of «à les» (for plural nouns).
In Spanish, a means to or towards.
In Portuguese, it is either the feminine definite article or a preposition meaning "to", "toward".
In Greek, a- is a prefix (alpha privativum) meaning "not" or "devoid of," used in many borrowed words in English, German and Romance languages (for example, amoral, asexual, arhythmic).
A (kana), the Japanese kana あ and ア which may be used to represent Asia.
In Esperanto as well as in Ido, -a is the adjectival/attributive ending; A is commonly an abbreviation meaning English (language).
In Interlingua, a means at or to.

Other

In American Major League Baseball,
- The Oakland Athletics are often simply referred to as the "A's."
- A can stand for Appearances or Assist.
In calendars, A is often an abbreviation for the months April and August.
In education, a grade of A typically represents the highest score that students can achieve. This is sometimes coupled with a plus/minus sign, as in A+ or A-, or a number, as in A1. It is occasionally a grade one level below A* (pronounced "A Star"). In Colombia, Finland, and New Zealand, A is the grade above a fail in a Pass ("Approve")/Fail test.
In finance, A is the U.S. ticker symbol for Agilent Technologies.
In games, the letter A is used to mark each of the Aces in a deck of playing cards.
In international licence plate codes, A stands for Austria.
In international paper sizes, A is a series of sizes with an aspect ratio of roughly 70% width to height, with A4 being an example popular size.
In photography, most SLR cameras use A to signify aperture priority mode, where the user sets the aperture and the camera determines the shutter speed.

Image:Anarchist s.png

A in the Anarchist Symbol

In political theory, an A in a full circle is an anarchist symbol.
As the first letter of a postal code,
- In Canada, A stands for Newfoundland and Labrador.
In radio,
- the NATO A band ranges below 0.25 GHz.
On the serial numbers of United States dollars, A identifies the Federal Reserve Bank of Boston.
In some sports, A is an abbreviation for Assists.
- A is also a term used to signify the standard of grade a certain team is in comparison to another team of the same age. e.g. John is in the A team for soccer.
In Christian theology, alpha is a metaphor for the beginning/creation of time and matter. It is sometimes translated to A.
As a timezone, A is the military designation for Coordinated Universal Time+1, also known as CET or Central European Time.
Topographically, A is used to describe an object shaped like the capital letter A, such as an A-frame.
A (New York City Subway service), a service of the New York City Subway.
A is a brassiere cup size.
A name intended for a Swedish child born in 1991.

A (disambiguation)

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