a definition | Dictionary.com

A, a

[ey]

–noun, plural A's or As, a's or as.

1.	the first letter of the English alphabet, a vowel.

2.	any spoken sound represented by the letter A or a, as in bake, hat, father, or small.

3.	something having the shape of an A.

4.	a written or printed representation of the letter A or a.

5.	a device, as a printer's type, for reproducing the letter A or a.

—Idioms

6.	from A to Z, from beginning to end; thoroughly; completely: He knows the Bible from A to Z.

7.	not know from A to B, to know nothing; be ignorant.

a

1 [uh; when stressed ey]

–indefinite article

1.	not any particular or certain one of a class or group: a man; a chemical; a house.

2.	a certain; a particular: one at a time; two of a kind; A Miss Johnson called.

3.	another; one typically resembling: a Cicero in eloquence; a Jonah.

4.	one (used before plural nouns that are preceded by a quantifier singular in form): a hundred men (compare hundreds of men); a dozen times (compare dozens of times).

5.	indefinitely or nonspecifically (used with adjectives expressing number): a great many years; a few stars.

6.	one (used before a noun expressing quantity): a yard of ribbon; a score of times.

7.	any; a single: not a one.

Origin:
ME; orig. preconsonantal phonetic var. of an ¹

Usage note:
In both spoken and written English the choice of a¹ or an ¹ is determined by the initial sound of the word that follows. Before a consonant sound, a is used; before a vowel sound, an: a book, a rose; an apple, an opera. Problems arise occasionally when the following word begins with a vowel letter but actually starts with a consonant sound, or vice versa. Some words beginning with the vowel letter u and all words beginning with the vowel letters eu are pronounced with a beginning consonant sound, as if the first letter were y: a union; a European. Some other spellings that begin with a vowel letter may also stand for an initial consonant sound: a ewe; a ewer. The words one and once and all compounds of which they are the first element begin with a w sound: a one-room apartment; a once-famous actor.
The names of the consonant letters f, h, l, m, n, r, s, and x are pronounced with a beginning vowel sound. When these letters are used as words or to form words, they are preceded by an: to rent an L-shaped studio; to fly an SST. The names of the vowel letter u and the semivowel letters w and y are pronounced with a beginning consonant sound. When used as words, they are preceded by a: a U-turn; The plumber installed a Y in the line.
In some words beginning with the letter h, the h is not pronounced; the words actually begin with a vowel sound: an hour; an honor. When the h is strongly pronounced, as in a stressed syllable at the beginning of a word, it is preceded by a: a history of the Sioux; a hero sandwich. (In former times an was used before strongly pronounced h in a stressed first syllable: an hundred.) Such adjectives as historic, historical, heroic, and habitual, which begin with an unstressed syllable and often with a silent or weakly pronounced h, are commonly preceded by an, especially in British English. But the use of a rather than an is widespread in both speech and writing: a historical novel; a habitual criminal. Hotel and unique are occasionally preceded by an, but this use is increasingly old-fashioned. Although in some dialects an has yielded to a in all cases, edited writing reflects usage as described above.

a

2 [uh; when stressed ey]

–preposition

each; every; per: ten cents a sheet; three times a day.

Origin:
orig. ME a, preconsonantal var. of on (see a- ¹ ); confused with a ¹

a

3 [uh]

–preposition

Pronunciation Spelling. a reduced, unstressed form of of (often written as part of a single, unhyphenated word): cloth a gold; time a day; kinda; sorta.

Origin:
ME; unstressed preconsonantal var. of of ¹

a

4 [uh]

–auxiliary verb Pronunciation Spelling.

a reduced, unstressed form of auxiliary have following some modals, as might, should, could, would, and must (usually written as part of a single, unhyphenated word): We shoulda gone.

Compare of ²

Origin:
ME; phonetic var. of have

a

5 [uh, a, ah]

–pronoun British Dialect.

he.

she.

it.

they.

Origin:
ME a, ha

a'

[ah, aw]

–adjective

Scot. all: for a' that.

Also, a.

A

1.	Electricity. ampere; amperes.

2.	Physics. angstrom.

answer.

4.	British. arterial (used with a road number to designate a major highway): Take the A525 to Ruthin.

A

Symbol.

1.	the first in order or in a series.

2.	(sometimes lowercase) (in some grading systems) a grade or mark, as in school or college, indicating the quality of a student's work as excellent or superior.

3.	(sometimes lowercase) (in some school systems) a symbol designating the first semester of a school year.

Music.

a.	the sixth tone in the scale of C major or the first tone in the relative minor scale, A minor.

b.	a string, key, or pipe tuned to this tone.

c.	a written or printed note representing this tone.

d.	(in the fixed system of solmization) the sixth tone of the scale of C major, called la.

e.	the tonality having A as the tonic note.

5.	Physiology. a major blood group, usually enabling a person whose blood is of this type to donate blood to persons of group A or AB and to receive blood from persons of O or A. Compare ABO system.

6.	(sometimes lowercase) the medieval Roman numeral for 50 or 500. Compare Roman numerals.

7.	Chemistry. (formerly) argon.

8.	Chemistry, Physics. mass number.

Biochemistry.

adenine.

alanine.

10.	Logic. universal affirmative.

11.	British. a designation for a motion picture recommended as suitable for adults. Compare AA (def. 5), U (def. 5), X (def. 9).

12.	a proportional shoe width size, narrower than B and wider than AA.

13.	a proportional brassiere cup size, smaller than B and larger than AA.

14.	a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.

a

Measurements.

are; ares.

a

Symbol, Logic.

universal affirmative.

Å

Symbol, Physics.

angstrom.

A-

atomic (used in combination): A-bomb; A-plant.

a-

a reduced form of the Old English preposition on, meaning “on,” “in,” “into,” “to,” “toward,” preserved before a noun in a prepositional phrase, forming a predicate adjective or an adverbial element (afoot; abed; ashore; aside; away), or before an adjective (afar; aloud; alow), as a moribund prefix with a verb (acknowledge), and in archaic and dialectal use before a present participle in -ing (set the bells aringing); and added to a verb stem with the force of a present participle (ablaze; agape; aglow; astride; and originally, awry).

Origin:
ME, late OE; cf. a ² , nowadays

a-

a reduced form of the Old English preposition of: akin; afresh; anew.

Origin:
ME; see a ³

a-

an old point-action prefix, not referring to an act as a whole, but only to the beginning or end: She arose (rose up). They abided by their beliefs (remained faithful to the end).

Origin:
ME; OE a- (unstressed), ǣ-, ā-, ō- (stressed; see abb, woof ¹ , oakum ), rarely or- (see ordeal ) ≪ Gmc *uz- < unstressed IE *uss- < *ud-s, akin to out; in some cases confused with a- ⁴ , as in abridge

a-

var. of ab- before p and v: aperient; avert.

Origin:
ME < L ā-, a- (var. of ab- ab- ); in some words < F a- < L ab-, as in abridge

a-

var. of ad-, used: (1) before sc, sp, st (ascend) and (2) in words of French derivation (often with the sense of increase, addition): amass.

Origin:
ME, in some words < MF a- < L ad- prefix or ad prep. (see ad- ), as in abut; in others < L a- (var. of ad- ad- ), as in ascend

a-

var. of an- ¹ before a consonant, meaning “not,” “without”: amoral; atonal; achromatic.

-a

a plural ending of nouns borrowed from Greek and Latin: phenomena; criteria; data; errata; genera.

-a

a feminine singular ending of nouns borrowed from Latin and Greek, also used in Neo-Latin coinages to Latinize bases of any origin, and as a Latin substitute for the feminine ending -ē of Greek words: anabaena; cinchona; pachysandra.

-a

an ending of personal names forming feminines from masculines: Georgia; Roberta.

Origin:
< L fem. -a (see -a ² ), as Claudia, fem. of Claudius

-a

a suffix designating the oxide of the chemical element denoted by the stem: alumina; ceria; thoria.

Origin:
prob. generalized from the -a of magnesia

A.

Absolute.

Academy.

3.	acre; acres.

America.

American.

angstrom.

7.	year. Origin: < L annō, abl. of annus

answer.

9.	before. Origin: < L ante

10.

April.

11.	Artillery.

a.

about.

2.	acre; acres.

active.

4.	adjective.

alto.

6.	ampere; amperes.

7.	year. Origin: < L annō, abl. of annus

8.	anonymous.

answer.

10.	before. Origin: < L ante

11.	are; ares.

12.	Baseball. assist; assists.

ab-

a formal element occurring in loanwords from Latin, where it meant “away from”: abdicate; abolition.

Also, a-, abs-.

Origin:
< L ab (prep. and prefix) from, away, c. Gk apó, Skt ápa, G ab, E of ¹ , off

an-

a prefix occurring before stems beginning with a vowel or h in loanwords from Greek, where it means “not,” “without,” “lacking” (anarchy; anecdote); used in the formation of compound words: anelectric.

Also, before a consonant, a-.

Origin:
< Gk. See a- ⁶ , in- ³ , un- ¹

Bron⋅zi⋅no

[brawn-dzee-naw]

–noun

A⋅gno⋅lo (di Co⋅si⋅mo di Ma⋅ria⋅no) [ah-nyaw-law dee kaw-zee-maw dee mah-ryah-naw]

, 1502–72, Italian painter.

Young

[yuhng]

–noun

1.	Andrew (Jackson, Jr.), born 1932, U.S. clergyman, civil-rights leader, politician, and diplomat: mayor of Atlanta, Georgia, since 1981.

2.	Art(hur Henry), 1866–1944, U.S. cartoonist and author.

3.	Brigham, 1801–77, U.S. leader of the Church of Jesus Christ of Latter-day Saints.

4.	Charles, 1864–1922, U.S. army colonel: highest-ranking black officer in World War I.

5.	Denton T. (Cy), 1867–1955, U.S. baseball player.

6.	Edward, 1683–1765, English poet.

7.	Ella, 1867–1956, Irish poet and mythologist in the U.S.

8.	Lester Willis (“Pres”; “Prez”), 1909–59, U.S. jazz tenor saxophonist.

9.	Owen D., 1874–1962, U.S. lawyer, industrialist, government administrator, and financier.

10.	Stark, 1881–1963, U.S. drama critic, novelist, and playwright.

11.	Thomas, 1773–1829, English physician, physicist, mathematician, and Egyptologist.

12.	Whitney M., Jr., 1921–71, U.S. social worker and educator: executive director of the National Urban League 1961–71.

Link To a

a¹ or A (ā)

n. pl. a's or A's also as or As

The first letter of the modern English alphabet.
Any of the speech sounds represented by the letter a.
The first in a series.
Something shaped like the letter A.
A The best or highest in quality or rank: grade A milk.
Music
1. The sixth tone in the scale of C major or the first tone in the relative minor scale.
2. A key or scale in which A is the tonic.
3. A written or printed note representing this tone.
4. A string, key, or pipe tuned to the pitch of this tone.
A One of the four major blood groups in the ABO system. Individuals with this blood group have the A antigen on the surface of their red blood cells, and the anti-B antibody in their blood serum.

a² (ə; ā when stressed)

indef.art.

Used before nouns and noun phrases that denote a single but unspecified person or thing: a region; a person.
Used before terms, such as few or many, that denote number, amount, quantity, or degree: only a few of the voters; a bit more rest; a little excited.
1. Used before a proper name to denote a type or a member of a class: the wisdom of a Socrates.
2. Used before a mass noun to indicate a single type or example: a dry wine.
The same: birds of a feather.
Any: not a drop to drink.

[Middle English, variant of an, an; see an¹.]

Usage Note: In writing, the form a is used before a word beginning with a consonant sound, regardless of its spelling (a frog, a university). The form an is used before a word beginning with a vowel sound (an orange, an hour). · An was once a common variant before words beginning with h in which the first syllable was unstressed; thus 18th-century authors wrote either a historical or an historical but a history, not an history. This usage made sense in that people often did not pronounce the initial h in words such as historical and heroic, but by the late 19th century educated speakers usually pronounced initial h, and the practice of writing an before such words began to die out. Nowadays it survives primarily before the word historical. One may also come across it in the phrases an hysterectomy or an hereditary trait. These usages are acceptable in formal writing.

a³ (ə)

prep. In every; to each; per: once a month; one dollar a pound.

[Middle English, from Old English an, in; see on.]

a⁴ (ə)

aux.v. Informal
Have: He'd a come if he could.

[Middle English, alteration of haven, to have; see have.]

a⁵
abbr.

acceleration
are (measurement)

A
abbr.

accusative
Games ace
across
adenine
alto
ampere
or Å angstrom
area

ac·cel·er·a·tion (āk-sěl'ə-rā'shən)

1. The act of accelerating.
2. The process of being accelerated.
Abbr. a Physics The rate of change of velocity with respect to time.

ad·e·nine (ād'n-ēn', -ĭn)

n. Abbr. A
A purine base, C₅H₅N₅, that is the constituent involved in base pairing with thymine in DNA and with uracil in RNA.

al·to (āl'tō)

n. pl. al·tos

A low female singing voice; a contralto.
A countertenor.
1. The range between soprano and tenor.
2. A singer whose voice lies within this range.
3. An instrument that sounds within this range.
4. Abbr. A A vocal or instrumental part written in this range.

[Italian, from Latin altus, high; see al-² in Indo-European roots.]

am·pere (ām'pîr')

n. Abbr. A

A unit of electric current in the meter-kilogram-second system. It is the steady current that when flowing in straight parallel wires of infinite length and negligible cross section, separated by a distance of one meter in free space, produces a force between the wires of 2 × 10^-7 newtons per meter of length.
A unit in the International System specified as one International coulomb per second and equal to 0.999835 ampere. See Table at measurement.

[After André Marie Ampère.]

ang·strom or ång·strom (āng'strəm)

n. Abbr. A or Å or angst
A unit of length equal to one hundred-millionth (10^-8) of a centimeter, used especially to specify radiation wavelengths. Also called angstrom unit. See Table at measurement.

[After Anders Jonas Ångström.]

are² (âr, är)

n. Abbr. a
A metric unit of area equal to 100 square meters (119.6 square yards).

[French, from Latin ārea, open space; see area.]

ar·e·a (âr'ē-ə)

(click for larger image in new window)
n.

A roughly bounded part of the space on a surface; a region: a farming area; the New York area.
A surface, especially an open, unoccupied piece of ground: a landing area; a playing area.
A distinct part or section, as of a building, set aside for a specific function: a storage area in the basement.
A division of experience, activity, or knowledge; a field: studies in the area of finance; a job in the health-care area.
An open, sunken space next to a building; an areaway.
Abbr. A The extent of a planar region or of the surface of a solid measured in square units.
Computer Science A section of storage set aside for a particular purpose.

[Latin ārea, open space; possibly akin to ārēre, to be dry; see arid.]
ar'e·al adj., ar'e·al·ly adv.

A\ (named [=a] in the English, and most commonly ["a] in other languages). The first letter of the English and of many other alphabets. The capital A of the alphabets of Middle and Western Europe, as also the small letter (a), besides the forms in Italic, black letter, etc., are all descended from the old Latin A, which was borrowed from the Greek Alpha, of the same form; and this was made from the first letter (?) of the Ph[oe]nician alphabet, the equivalent of the Hebrew Aleph, and itself from the Egyptian origin. The Aleph was a consonant letter, with a guttural breath sound that was not an element of Greek articulation; and the Greeks took it to represent their vowel Alpha with the ["a] sound, the Ph[oe]nician alphabet having no vowel symbols. This letter, in English, is used for several different vowel sounds. See Guide to pronunciation, [sect][sect] 43-74. The regular long a, as in fate, etc., is a comparatively modern sound, and has taken the place of what, till about the early part of the 17th century, was a sound of the quality of ["a] (as in far).

2. (Mus.) The name of the sixth tone in the model major scale (that in C), or the first tone of the minor scale, which is named after it the scale in A minor. The second string of the violin is tuned to the A in the treble staff. -- A sharp (A[sharp]) is the name of a musical tone intermediate between A and B. -- A flat (A[flat]) is the name of a tone intermediate between A and G.

A per se (L. per se by itself), one pre["e]minent; a nonesuch. [Obs.]

O fair Creseide, the flower and A per se Of Troy and Greece. --Chaucer.

A\ ([.a] emph. [=a]). 1. [Shortened form of an. AS. [=a]n one. See One.] An adjective, commonly called the indefinite article, and signifying one or any, but less emphatically. "At a birth"; "In a word"; "At a blow". --Shak.

Note: It is placed before nouns of the singular number denoting an individual object, or a quality individualized, before collective nouns, and also before plural nouns when the adjective few or the phrase great many or good many is interposed; as, a dog, a house, a man; a color; a sweetness; a hundred, a fleet, a regiment; a few persons, a great many days. It is used for an, for the sake of euphony, before words beginning with a consonant sound [for exception of certain words beginning with h, see An]; as, a table, a woman, a year, a unit, a eulogy, a ewe, a oneness, such a one, etc. Formally an was used both before vowels and consonants.

2. [Originally the preposition a (an, on).] In each; to or for each; as, "twenty leagues a day", "a hundred pounds a year", "a dollar a yard", etc.

A\ ([.a]), prep. [Abbreviated form of an (AS. on). See On.]

1. In; on; at; by. [Obs.] "A God's name." "Torn a pieces." "Stand a tiptoe." "A Sundays" --Shak. "Wit that men have now a days." --Chaucer. "Set them a work." --Robynson (More's Utopia).

2. In process of; in the act of; into; to; -- used with verbal substantives in -ing which begin with a consonant. This is a shortened form of the preposition an (which was used before the vowel sound); as in a hunting, a building, a begging. "Jacob, when he was a dying" --Heb. xi. 21. "We'll a birding together." " It was a doing." --Shak. "He burst out a laughing." --Macaulay.

Note: The hyphen may be used to connect a with the verbal substantive (as, a-hunting, a-building) or the words may be written separately. This form of expression is now for the most part obsolete, the a being omitted and the verbal substantive treated as a participle.

A\ [From AS. of off, from. See Of.] Of. [Obs.] "The name of John a Gaunt." "What time a day is it ?" --Shak. "It's six a clock." --B. Jonson.

A\ A barbarous corruption of have, of he, and sometimes of it and of they. "So would I a done" "A brushes his hat." --Shak.

A\ An expletive, void of sense, to fill up the meter

A merry heart goes all the day, Your sad tires in a mile-a. --Shak.

Language Translation for : a

Spanish: la,

German: das A, musik. Note,

Japanese: イ調

More Translations »

a (1)

indefinite article, c.1150, a variation of O.E. an (see an) in which the -n- began to disappear before consonants, a process mostly complete by 1340. The -n- also was retained before words beginning with a sounded -h- until c.1600; it still is retained by many writers before unaccented syllables in h- or (e)u-, but is now no longer normally spoken as such. The -n- also lingered (especially in southern England dialect) before -w- and -y- through 15c.

a (2)

as in twice a day, etc., is from O.E. an "on," in this case "on each." The sense was extended from time to measure, price, place, etc. The habit of tacking a onto a gerund (as in a-hunting we will go) died out 18c.

A

A Nasdaq stock symbol specifying that the stocks are Class "A" shares of the company.

Investopedia Commentary

Nasdaq-listed securities have four or five characters. If a fifth letter appears, it identifies the issue as other than a single issue of common stock or capital stock.