A

A (uppercase) or a (lowercase) is the first letter and the first vowel of the modern English alphabet and of the ISO basic Latin alphabet. Its English name is spelled "a" and pronounced /eɪ/, with the plural "aes," a form that is rarely used. The letter descends, through an unbroken chain of adaptation, from the Phoenician letter aleph, which itself originated in an Egyptian hieroglyph depicting an ox's head, giving A a recorded history of well over three thousand years. Today it is employed, in one form or another, by hundreds of languages written in the Latin script, and in English text it ranks as the third most frequent letter, after E and T, accounting for roughly 8.2 percent of all letters written.

Origins in Ancient Scripts

The conventional account of the letter's origin traces it to an Egyptian hieroglyph representing the head of an ox. Around 1900–1700 BC, Semitic-speaking workers in Egypt and the Sinai Peninsula adapted a small set of hieroglyphic signs into an alphabetic writing system now known as Proto-Sinaitic or Proto-Canaanite. The ox-head sign was assigned to the initial consonant of the Semitic word for "ox," ʾalp, so that the letter acquired both its name — aleph — and its alphabetic value through the principle of acrophony, in which a picture stands for the first sound of the word it depicts.

The Phoenicians, inheritors and systematizers of the early Canaanite scripts, included aleph in their consonantal alphabet by around 1050 BC. In Phoenician, aleph represented the glottal stop /ʔ/, a consonantal sound, and its graphic form resembled an ox's head lying on its side, with the horns pointing upward or to one side. The Phoenician shape became the immediate model for the letter as it passed to the Greeks.

Transmission Through Greek, Etruscan, and Latin

When Greek speakers adopted the Phoenician alphabet, probably through trade contacts in the early first millennium BC, they renamed the letter alpha. Because Greek possessed no glottal stop, they reassigned aleph to the low vowel sound, and alpha served in Greek for both short /a/ and long /aː/. In many of the earliest Greek inscriptions the letter still lay on its side in the Phoenician manner; over time, Greek scribes stabilized an upright, symmetrical triangular form with a horizontal bar — essentially the shape of the modern capital A.

The alphabet reached Italy through Greek colonists, notably the Euboean variant used at Cumae, and the Etruscans adopted the letter, retaining its vowel value. The Latin alphabet in turn developed from Etruscan practice, and the monumental Roman capitals of the late Republic and early Empire fixed the uppercase A in the form still used today. In classical Latin, A represented short /a/ and long /aː/, and it occurred in some of the most basic words of the language, such as amo ("I love") and aqua ("water").

Development of the Lowercase and Typographic Forms

The lowercase a emerged gradually from Roman cursive writing. In late antiquity, scribes simplified the angular capital into a rounded form, and the uncial scripts of the fourth to eighth centuries produced a soft, single-bowl letter. The double-storey lowercase "a," with its distinctive upper bowl and curved stem, was consolidated in the Carolingian minuscule developed in the late eighth century under Charlemagne's educational reforms and later revived by Italian humanist scribes. When movable-type printing appeared in Europe in the mid-fifteenth century, printers based their romans on these humanist forms, making the double-storey a standard in most serif typefaces. A single-storey variant, written "ɑ," survives in everyday handwriting and in some geometric sans-serif designs, such as Futura. Typographers have long regarded A as one of the most structurally stable letters, its triangular form appearing in monumental architecture, logos, and mountain-themed symbolism.

Pronunciation and Use in English

In present-day English, the letter corresponds to an unusually wide range of vowel sounds, largely as a result of historical sound changes, most notably the Great Vowel Shift of roughly 1400–1700, during which Middle English long /aː/ (as in "name") rose to modern /eɪ/. Principal values include:

• the short vowel /æ/ in words such as "cat" and "hand";
• the broad vowel /ɑː/ in "father," "palm," and "spa";
• back rounded or long vowels before l and labial consonants, as in "tall," "all," "water," and "watch";
• the so-called long a /eɪ/ in "name," "late," and "ale";
• the reduced schwa /ə/ in unstressed syllables, as in "about" and "sofa";
• sporadic /ɛ/ in words such as "any," "many," and "said."

The letter also participates in numerous digraphs: "ai" and "ay" usually represent /eɪ/ ("rain," "day"); "au" and "aw" usually represent /ɔː/ ("author," "saw"); and "ea" is highly variable ("meat" /iː/, "head" /ɛ/, "great" /eɪ/, "heart" /ɑː/).

As an independent word, "a" is the English indefinite article, historically a weakened form of the numeral "one" (older "an"). It appears as "a" before consonant sounds and "an" before vowel sounds, and is normally pronounced as an unstressed schwa.

The Letter Across Other Languages

Throughout the Latin-script world, A almost invariably denotes some kind of low, unrounded vowel — /a/, /ɑ/, /æ/, or a reduced variant. It is pronounced /a/ in Spanish, Italian, and most Slavic languages; /a/ or /ɑ/ in French; /a/ or /aː/ in German and Dutch; and carries length distinctions in languages such as Finnish, Hungarian, and Czech. Scandinavian languages add å for a rounded /ɔ/-like sound, while Danish, Norwegian, and Icelandic use æ.

A rich set of diacritically marked variants exists: á and à in French, Spanish, Portuguese, and Italian; ä in German, Swedish, Finnish, and Slovak; â and ã in Portuguese and Romanian and French; ą, a nasal vowel, in Polish; ă, a schwa-like sound, in Romanian; ā in Latvian and Maori; and Vietnamese a, ă, and â, which distinguish several different vowels. Related characters include the ligature Æ (ash), formed from a and e in Old English and modern North Germanic orthographies; the Cyrillic letter А, taken directly from Greek alpha and used in Russian, Ukrainian, Bulgarian, and other languages; and the Elder Futhark rune ansuz (ᚨ), generally regarded as derived from an alpha-like form. The International Phonetic Alphabet employs a family of A-based symbols — /a/, /ä/, /ɑ/, /æ/, /ɐ/, and the turned a /ə/ (schwa) — for its lowest vowel categories.

Uses in Science, Mathematics, and Computing

Because it heads the alphabet, A is the default choice for the first item in any sequence, and it has acquired dense technical meanings across the disciplines:

• Mathematics: A commonly denotes an unknown or given quantity, a set (as in "set A"), or a matrix (matrix A); it is the standard symbol for area, as in A = πr².
• Physics and metrology: A is the symbol for the ampere, the SI base unit of electric current; Å denotes the ångström, 10⁻¹⁰ metre; lowercase a is the symbol for the SI prefix atto- (10⁻¹⁸) and for the unit of area called the are (100 m²