A (named a /?e?/, plural aes) is the first letter and vowel in the ISO basic Latin alphabet. It is similar to the Ancient Greek letter alpha, from which it derives. The upper-case version consists of the two slanting sides of a triangle, crossed in the middle by a horizontal bar. The lower-case version can be written in two forms: the double-storey a and single-storey ?. The latter is commonly used in handwriting and fonts based on it, especially fonts intended to be read by children. It is also found in italic type.
The earliest certain ancestor of "A" is aleph (also written aleph), the first letter of the Phoenician alphabet (which consisted entirely of consonants, thereby being an abjad rather than a true alphabet). In turn, the origin of aleph may have been a pictogram of an ox head in proto-Sinaitic script influenced by Egyptian hieroglyphs, styled as a triangular head with two horns extended.
In 1600 B.C.E., the Phoenician alphabets letter had a linear form that served as the base for some later forms. Its name must have corresponded closely to the Hebrew or Arabic aleph.
When the ancient Greeks adopted the alphabet, they had no use for the glottal stop—the first phoneme of the Phoenician pronunciation of the letter, and the sound that the letter denoted in Phoenician and other Semitic languages—so they used an adaptation of the sign to represent the vowel /a/, and gave it the similar name of 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 their civilization in the Italian Peninsula and left the letter unchanged. The Romans later adopted the Etruscan alphabet to write the Latin language, and the resulting letter was preserved in the Latin alphabet used to write many languages, including English.
During Roman times, there were many variations on the letter "A". First was the monumental or lapidary style, which was used when inscribing on stone or other "permanent" mediums. For perishable surfaces, which were used for everyday or utilitarian purposes, a cursive style was used. Due to the "perishable" nature of the surfaces, examples of this style are not as common as those of the monumental. This perishable style was called cursive and numerous variations have survived, such as majuscule cursive, minuscule cursive, and semicursive minuscule. There were also variants intermediate between the monumental and the cursive. The known variants include the early semi-uncial, the uncial, and the later semi-uncial.
At the end of the Roman Empire (5th century AD), several variants of the cursive minuscule developed through Western Europe. Among these were the semicursive minuscule of Italy, the Merovingian script in France, the Visigothic script in Spain, and the Insular or Anglo-Irish semi-uncial or Anglo-Saxon majuscule, of Great Britain. By the 9th century, the Caroline script, which was very similar to the present-day form, was the principal form used in book-making, before the advent of the printing press. This form was derived through a combining of prior forms.
15th-century Italy saw the formation of the two main variants that are known today. These variants, the Italic and Roman forms, were derived from the Caroline Script version. The Italic form used in most current handwriting consists of a circle and vertical stroke ("?"), called Latin alpha or "script a". This slowly developed from the fifth-century form resembling the Greek letter tau in the hands of medieval Irish and English writers. Most printed material uses the Roman 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.
In modern English orthography, the letter A represents six different vowel sounds: A by itself frequently denotes the near-open front unrounded vowel (/ae/) as in pad; the open back unrounded vowel (/??/) as in father, its original, Latin and Greek, sound; a closer, further fronted sound as in "hare", which developed as the sound progressed from "father" to "ace"; in concert with a later orthographic vowel, the diphthong /e?/ as in ace and major, due to effects of the Great Vowel Shift; the more rounded form in "water" or its closely related cousin, found in "was".
The double "a" sequence does not occur in native English words; however, it is found in some words derived from foreign languages such as Aaron and aardvark.
"A" is the third-most-commonly used letter in English (after "E" and "T"), and the second most common in Spanish and French. In one study, on average, about 3.68% of letters used in English texts tend to be a, while the number is 6.22% in Spanish and 3.95% in French.
In most languages that use the Latin alphabet, A denotes an open unrounded vowel, such as /a/, /a/, or /?/. An exception is Saanich, in which A (and A) stands for a close-mid front unrounded vowel /e/.
In algebra, the letter "A" along with other letters at the beginning of the alphabet is used to represent known quantities, whereas the letters at the end of the alphabet (x,y,z) are used to denote unknown quantities.
In geometry, capital A, B, C etc. are used to denote segments, lines, rays, etc. A capital A is also typically used as one of the letters to represent an angle in a triangle, the lowercase a representing the side opposite angle A.
In logic, A is used to signify the universal affirmative.
In physics, A is the SI unit symbol for Ampere.
In phonetic and phonemic notation:in the International Phonetic Alphabet, [a] is used for the open front unrounded vowel, [a] is used for the open central unrounded vowel and [?] is used for the open back unrounded vowel.
in X-SAMPA, [a] is used for the open front unrounded vowel and [A] is used for the open back unrounded vowel.
"A" is often used to denote something or someone of a better or more prestigious quality or status: A-, A or A+, the best grade that can be assigned by teachers for students schoolwork; "A grade" for clean restaurants; A-list celebrities, etc. Such associations can have a motivating effect, as exposure to the letter A has been found to improve performance, when compared with other letters.
A is a common symbol of school and basic phonetics in the US, along with B and C.
Finally, the letter A is used to denote size, as in a narrow size shoe, or a small cup size in a brassiere.? ? : Greek letter alpha
? ? : Cyrillic letter A
? ? : Latin letter alpha / script A
a : a turned lowercase letter A, used by the International Phonetic Alphabet for the near-open central vowel
? : a turned capital letter A, used in predicate logic to specify universal quantification ("for all")
ª : an ordinal indicator
AE ae : Latin AE ligature
A a : A letter used in various Scandinavian (and other) languages
1 Also for encodings based on ASCII, including the DOS, Windows, ISO-8859 and Macintosh families of encodings.