[ uh; when stressed ey ]
See synonyms for a on Thesaurus.com
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.

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

  2. 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).

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

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

  5. any; a single: not a one.

Origin of a

First recorded in 1200–50; Middle English; originally preconsonantal phonetic variant of an1

Grammar notes for a

In both spoken and written English the choice of a1 or an1 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.

Other definitions for a (2 of 28)

[ uh; when stressed ey ]

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

Origin of a

Originally Middle English a, preconsonantal variant of on (see a-1); confused with a1

Other definitions for a (3 of 28)

[ uh ]

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

Origin of a

Middle English; unstressed preconsonantal variant of of1

Other definitions for a (4 of 28)

[ uh ]

auxiliary verbInformal.
  1. 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.

Origin of a

First recorded in 1300–50; Middle English; a phonetic variant of have

Other definitions for a (5 of 28)

[ uh, a, ah ]

pronounBritish Dialect.
  1. he1.

  2. she.

  1. it1.

  2. I2.

Origin of a

First recorded in 1200–50; Middle English a, ha

Other definitions for a (6 of 28)


  1. are; ares.

Other definitions for a' (7 of 28)


or a

[ ah, aw ]

  1. all: for a' that.

Other definitions for A (8 of 28)


or 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.

  1. something having the shape of an A.

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

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

Other definitions for A (9 of 28)


  1. Electricity. ampere; amperes.

  2. Physics. angstrom; angstroms.

  1. answer.

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

Other definitions for A (10 of 28)


  1. the first in order or in a series.

  2. Sometimes a .

    • (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.

    • (in some school systems) a symbol designating the first semester of a school year.

  1. Music.

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

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

    • a written or printed note representing this tone.

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

    • the tonality having A as the tonic note.

  2. 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.

  3. Sometimes a . the medieval Roman numeral for 50 or 500.: Compare Roman numerals.

  4. Chemistry. (formerly) argon.

  5. Chemistry, Physics. mass number.

  6. Biochemistry.

  7. Also a .Logic. universal affirmative.

  8. British. a designation for a motion picture recommended as suitable for adults.: Compare AA2 (def. 5), U5 (def. 6), X3 (def. 9).

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

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

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

Other definitions for a- (11 of 28)


  1. 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 of a-

Middle English, late Old English; cf. a2, nowadays

Other definitions for a- (12 of 28)


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

Origin of a-

Middle English; see a3

Other definitions for a- (13 of 28)


  1. 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 of a-

Middle English; Old English a- (unstressed), ǣ-, ā-, ō- (stressed; see abb, woof1, oakum), rarely or- (see ordeal), ultimately from unattested Germanic uz- from unstressed Indo-European uss-, from ud-s (these latter two also unattested), akin to out; in some cases confused with a-4, as in abridge

Other definitions for a- (14 of 28)


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

Origin of a-

Middle English <Latin ā-, a- (variant of ab-ab-); in some words <French a-<Latin ab-, as in abridge

Other definitions for a- (15 of 28)


  1. variant 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 of a-

Middle English, in some words <Middle French a-<Latin ad- prefix or ad preposition (see ad-), as in abut; in others <Latin a- (variant of ad-ad-), as in ascend

Other definitions for a- (16 of 28)


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

Other definitions for A- (17 of 28)


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

Other definitions for -a (18 of 28)


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

Other definitions for -a (19 of 28)


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

Other definitions for -a (20 of 28)


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

Origin of -a

From Latin feminine ending -a, as Claudia, feminine of Claudius; see -a2

Other definitions for -a (21 of 28)


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

Origin of -a

Probably generalized from the -a of magnesia

Other definitions for Å (22 of 28)


Symbol, Physics.
  1. angstrom.

Other definitions for a. (23 of 28)


  1. year.

Origin of a.

<Latin annō, ablative of annus

Other definitions for a. (24 of 28)


  1. before.

Origin of a.

From the Latin word ante

Other definitions for a. (25 of 28)


  1. about.

  2. acre; acres.

  1. active.

  2. adjective.

  3. alto.

  4. ampere; amperes.

  5. anonymous.

  6. answer.

  7. are; ares.

  8. Baseball. assist; assists.

Other definitions for A. (26 of 28)


  1. year.

Origin of A.

<Latin annō, ablative of annus

Other definitions for A. (27 of 28)


  1. before.

Origin of A.

From the Latin word ante

Other definitions for A. (28 of 28)


  1. Absolute.

  2. Academy.

  1. acre; acres.

  2. America.

  3. American.

  4. angstrom.

  5. answer.

  6. April.

  7. Artillery.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use a in a sentence

  • Now-a-days it is the bankrupt who flouts, and his too confiding creditors who are jeered and laughed at.

    Glances at Europe | Horace Greeley
  • He felt himself the meanest, vilest thing a-crawl upon this sinful earth, and she—dear God!

    St. Martin's Summer | Rafael Sabatini
  • All that scientific bric-a-brac in the cupboard had far better be thrown away.

    The Salvaging Of Civilisation | H. G. (Herbert George) Wells
  • Urinary sediments may be studied under three heads: a. Unorganized sediments.

    A Manual of Clinical Diagnosis | James Campbell Todd
  • I knowed, a-course, that I could go kick up a fuss when Simpson stopped by his office on his trip back from Goldstone.

    Alec Lloyd, Cowpuncher | Eleanor Gates

British Dictionary definitions for a (1 of 11)


/ (ə, stressed or emphatic ) /

determiner(indefinite article; used before an initial consonant)
  1. used preceding a singular countable noun, if the noun is not previously specified or known: a dog; a terrible disappointment

  2. used preceding a proper noun to indicate that a person or thing has some of the qualities of the one named: a Romeo; a Shylock

  1. used preceding a noun or determiner of quantity: a cupful; a dozen eggs; a great many; to read a lot

  2. used preceding a noun indicating a concrete or abstract thing capable of being divided: half a loaf; a quarter of a minute

  3. (preceded by once, twice, several times, etc) each or every; per: once a day; fifty pence a pound

  4. a certain; one: to change policy at a stroke; a Mr Jones called

  5. (preceded by not) any at all: not a hope

British Dictionary definitions for a (2 of 11)


/ (ə) /

  1. an informal or dialect word for have they'd a said if they'd known

British Dictionary definitions for a (3 of 11)


/ (ə) /

  1. (usually linked to the preceding noun) an informal form of of sorta sad; a kinda waste

British Dictionary definitions for a (4 of 11)


symbol for
  1. acceleration

  2. are(s) (metric measure of land)

  1. atto-

British Dictionary definitions for a (5 of 11)



/ () /

nounplural a's, A's or As
  1. the first letter and first vowel of the modern English alphabet

  2. any of several speech sounds represented by this letter, in English as in take, bag, calm, shortage, or cobra

  1. Also called: alpha the first in a series, esp the highest grade or mark, as in an examination

  2. from A to Z from start to finish, thoroughly and in detail

British Dictionary definitions for a' (6 of 11)


aa or aw

/ (ɔː) /

  1. Scot variants of all

British Dictionary definitions for A (7 of 11)


symbol for
  1. music

    • a note having a frequency of 440 hertz (A above middle C) or this value multiplied or divided by any power of 2; the sixth note of the scale of C major

    • a key, string, or pipe producing this note

    • the major or minor key having this note as its tonic

  2. a human blood type of the ABO group, containing the A antigen

  1. (in Britain) a major arterial road: the A3 runs from London to Portsmouth

  2. (formerly, in Britain)

    • a film certified for viewing by anyone, but which contains material that some parents may not wish their children to see

    • (as modifier): an A film

  3. mass number

  4. the number 10 in hexadecimal notation

  5. cards ace

  6. chem argon (now superseded by Ar)

  7. ampere(s)

  8. Also: at ampere-turn

  9. absolute (temperature)

  10. (in circuit diagrams) ammeter

  11. area

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

  13. chem affinity

  14. biochem adenine

  15. logic a universal affirmative categorical proposition, such as all men are mortal: often symbolized as SaP: Compare E, I 2, O 1

    • a person whose job is in top management, or who holds a senior administrative or professional position

    • (as modifier): an A worker See also occupation groupings

abbreviation for
  1. Austria (international car registration)

Origin of A

from Latin a (ffirmo) I affirm

British Dictionary definitions for a- (8 of 11)


  1. not; without; opposite to: atonal; asocial

Origin of a-

from Greek a-, an- not, without

British Dictionary definitions for a- (9 of 11)


  1. on; in; towards: afoot; abed; aground; aback

  2. literary, or archaic (used before a present participle) in the act or process of: come a-running; go a-hunting

  1. in the condition or state of: afloat; alive; asleep

British Dictionary definitions for Å (10 of 11)


symbol for
  1. angstrom unit

British Dictionary definitions for A. (11 of 11)


abbreviation for
  1. acre(s) or acreage

  2. America(n)

  1. answer

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for A (1 of 3)


  1. Abbreviation of adenine, ampere, angstrom, area

Scientific definitions for a- (2 of 3)


  1. A prefix meaning “without” or “not” when forming an adjective (such as amorphous, without form, or atypical, not typical), and “absence of” when forming a noun (such as arrhythmia, absence of rhythm). Before a vowel or h it becomes an- (as in anhydrous, anoxia).

Scientific definitions for Å (3 of 3)


  1. Abbreviation of angstrom

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.