- "A"-shaped object: something shaped like a letter "A"
- In music, "A" is the 6th note in c major: the sixth note of a scale in c major. The A above middle c is often used to tune instruments and is standardized at a frequency of 440 hertz. Graphic representation of the tone of A
- In medicine, "A" is a human blood type of the ABO system containing the A antigen. Somebody with this type of blood can donate to people of the same group or of the ab group, and can receive blood from people with this type or with type O.
- For other uses of "A", see A (disambiguation).
Aa Bb cc Dd
Ww Xx Yy Zz
By 1600 BC, the Phoenician alphabet's letter had a linear form that served as the basis for some later forms. Its name must have corresponded closely to the Hebrew aleph. The name is also similar to the arabic alif.
When the ancient greeks adopted the alphabet, they had no use for the glottal stop that the letter had denoted in Phoenician and other Semitic languages, so they used the sign for the vowel /a/, and changed its name to alpha. In the earliest greek inscriptions after the greek Dark ages, dating to the 8th century BC, the letter rests upon its side, but in the greek alphabet of later times it generally resembles the modern capital letter, although many local varieties can be distinguished by the shortening of one leg, or by the angle at which the cross line is set.
The Etruscans brought the greek alphabet to what was Italy and left the letter unchanged. The romans later adopted the Etruscan alphabet to write latin, and the resulting letter was preserved in the modern latin alphabet used to write many languages, including english.
Blackletter A Uncial A Another Capital A
Modern roman A Modern Italic A Modern Script A The letter has two minuscule (lower-case) forms. The form used in most current handwriting consists of a circle and vertical stroke (ɑ). Most printed material uses a form consisting of a small loop with an arc over it (a). Both derive from the majuscule (capital) form. In greek handwriting, it was common to join the left leg and horizontal stroke into a single loop, as demonstrated by the Uncial version shown. Many fonts then made the right leg vertical. In some of these, the serif that began the right leg stroke developed into an arc, resulting in the printed form, while in others it was dropped, resulting in the modern handwritten form.
 usage In english, the letter "A" by itself usually denotes the near-open front unrounded vowel (/æ/) as in pad, the openfather, or, in concert with a later orthographic vowel, the diphthong /eɪ/ (though the pronunciation varies with the dialect) as in ace and major, due to effects of the Great vowel shift.
In most other languages that use the latin alphabet, the letter A denotes either an open back unrounded vowel (/ɑ/), or an open central unrounded vowel (/a/). In the international phonetic alphabet, variants of the letter A denote various vowels. In X-SAMPA, capital A denotes the open back unrounded vowel and lowercase a denotes the open front unrounded vowel.
A is the third-most common letter in english, and the second-most common in spanish and french. On average, about 3.6% of letters in english tend to be as, while the number is 6.2% in spanish and 4% in french.
The EBCDIC code for capital A is 193 and for lowercase a is 129.
 Meanings of A
A on the wall of the Drachenschlucht Eisenach, GermanyIn American major league baseball the Oakland athletics are often simply referred to as the "A's." A can stand for appearances or assist In astronomy, A stands for a whitish-blue class of stars in the Morgan-Keenan system A stands for 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). a is often used to denote the semi-major axis of an orbit In biochemistry, A is the symbol for alanine, adenine, and adenosine. Brassiere cup size A In calendars, A is often an abbreviation for the months April and august. In computing, <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. 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 electronics, A is a standard size of battery. A refers to the anode, or filament, component of a vacuum tube. In english, the word a is an indefinite article, see a, an In Esperanto, -a is the adjectival/attributive ending; A is commonly an abbreviation meaning english (language). 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. In finance, A is the U.S. ticker symbol for Agilent Technologies. 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 nouns) and «aux» is used in Place of «à les» (for plural nouns). In games, the letter A is used to mark each of the Aces in a deck of playing cards. In geology it stands for annum (latin for "year") and is usually used with Mega (Ma) and Giga (Ga) to indicate very long periods of time; see annum. 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). represent the continent asia. In india A is a movie rating, given to those intended to be seen only by adults. In Interlingua, a means at or to. 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 logic, the letter A is used as a symbol for the universal affirmative proposition in the general form "all x is y." The letters i, E, and O are used respectively for the particular affirmative "some x is y," the universal negative "no x is y," and the particular negative "some x is not y." The use of these letters is generally derived from the vowels of the two latin verbs affirmo (or AIo), "I assert," and nego, "I deny." The use of the symbols dates from the thirteenth century, though some authorities trace their origin to the greek logicians. In symbolic logic, the symbol ∀ (an inverted letter A) is the universal quantifier. In mathematics, A stands for area of geometric figures. A is often used as a digit meaning ten in hexadecimal and other positional numeral systems with a radix of 11 or greater, blackboard bold �dd38¸ (U+1D538 in Unicode), sometimes represents the algebraic numbers. In the On-line Encyclopedia of Integer sequences, each sequence has an id consisting of the letter A and six base 10 digits. In medicine, A (also, A+ or a-) is one of the human blood types. In music, A is a pitch class or note. A, or "side A," refers to the top or first side of a vinyl record. A is a British rock band, not to be confused with the a Band, an experimental group. A is an album by Jethro Tull. A is an album by Cass McCombs. In nutrition, A is a vitamin. 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. In physics: A can stand for: The mass number of an atom. The derived property of acceleration (upper-case A for an initial/constant accleration value; lower case a for an instantaneous acceleration variable.) The center of a hexagonal face of the Brillouin zone of a hexagonal lattice In poetry, A is the major work of influential twentieth century author louis Zukofsky. In political theory, an A in a full circle (Ⓐ) is an anarchist symbol. In portuguese, it is either the feminine definite article or a preposition meaning "to", "toward". 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 the si system of units, A is the symbol for the ampere or amp, the si base unit of electric current. a, atto, is the si prefix meaning 10−18 a is the symbol for one year, from the latin annum a is also the deprecated symbol for the are, a unit of surface area equal to 100 square metres. In spanish, a means to or towards. 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.