not any particular or certain one of a class or group: a man; a chemical; a house.
a certain; a particular: one at a time; two of a kind; A Miss Johnson called.
another; one typically resembling: a Cicero in eloquence; a Jonah.
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).
indefinitely or nonspecifically (used with adjectives expressing number): a great many years; a few stars.
one (used before a noun expressing quantity): a yard of ribbon; a score of times.
any; a single: not a one.
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)
each; every; per: ten cents a sheet; three times a day.
Other definitions for a (3 of 28)
Informal. a reduced, unstressed form of of (often written as part of a single, unhyphenated word): cloth a gold; time a day; kinda; sorta.
Other definitions for a (4 of 28)
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 of2.
Other definitions for a (5 of 28)
Other definitions for a (6 of 28)
Other definitions for a' (7 of 28)
all: for a' that.
Other definitions for A (8 of 28)
the first letter of the English alphabet, a vowel.
any spoken sound represented by the letter A or a, as in bake, hat, father, or small.
something having the shape of an A.
a written or printed representation of the letter A or a.
a device, as a printer's type, for reproducing the letter A or a.
Other definitions for A (9 of 28)
Other definitions for A (10 of 28)
the first in order or in a series.
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.
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.
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.
Sometimes a . the medieval Roman numeral for 50 or 500.: Compare Roman numerals.
Chemistry. (formerly) argon.
Chemistry, Physics. mass number.
Also a .Logic. universal affirmative.
a proportional shoe width size, narrower than B and wider than AA.
a proportional brassiere cup size, smaller than B and larger than AA.
a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.
Other definitions for a- (11 of 28)
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).
Other definitions for a- (12 of 28)
a reduced form of the Old English preposition of: akin; afresh; anew.
Other definitions for a- (13 of 28)
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).
Other definitions for a- (14 of 28)
Other definitions for a- (15 of 28)
Other definitions for a- (16 of 28)
Other definitions for A- (17 of 28)
atomic (used in combination): A-bomb; A-plant.
Other definitions for -a (18 of 28)
a plural ending of nouns borrowed from Greek and Latin: phenomena; criteria; data; errata; genera.
Other definitions for -a (19 of 28)
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)
an ending of personal names forming feminines from masculines: Georgia; Roberta.
Other definitions for -a (21 of 28)
a suffix designating the oxide of the chemical element denoted by the stem: alumina; ceria; thoria.
Other definitions for Å (22 of 28)
Other definitions for a. (23 of 28)
Other definitions for a. (24 of 28)
Other definitions for a. (25 of 28)
Baseball. assist; assists.
Other definitions for A. (26 of 28)
Other definitions for A. (27 of 28)
Other definitions for A. (28 of 28)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
How to use a in a sentence
ROME — What does it take for a Hollywood a-lister to get a private audience with Pope Francis?Pope Francis Has the Pleasure of Meeting Angelina Jolie for a Few Seconds | Barbie Latza Nadeau | January 8, 2015 | THE DAILY BEAST
Yes, Byrd—dead four-and-a-half years now—was a Kleagle in the Ku Klux Klan.Steve Scalise and the Right’s Ridiculous Racial Blame Game | Michael Tomasky | January 2, 2015 | THE DAILY BEAST
By the time it concluded with a sing-a-long of “XO,” Beyoncé had done the rare thing.Bow Down, Bitches: How Beyoncé Turned an Elevator Brawl Into a Perfect Year | Kevin Fallon | December 31, 2014 | THE DAILY BEAST
In another year, stories about the strange new face of an a-list actress might draw chortles and cackles.Renée Zellweger Got a New Face—and Everyone Had An Opinion About It | Kevin O’Keeffe | December 29, 2014 | THE DAILY BEAST
Because Duck Dynasty receives monster TV ratings and Robertson paid by a company (a&E) while making these public statements.Butts, Brawls, and Bill Cosby: The Biggest Celebrity Scandals of 2014 | Kevin Fallon | December 27, 2014 | THE DAILY BEAST
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)
used preceding a singular countable noun, if the noun is not previously specified or known: a dog; a terrible disappointment
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
used preceding a noun or determiner of quantity: a cupful; a dozen eggs; a great many; to read a lot
used preceding a noun indicating a concrete or abstract thing capable of being divided: half a loaf; a quarter of a minute
(preceded by once, twice, several times, etc) each or every; per: once a day; fifty pence a pound
a certain; one: to change policy at a stroke; a Mr Jones called
(preceded by not) any at all: not a hope
British Dictionary definitions for a (2 of 11)
an informal or dialect word for have they'd a said if they'd known
British Dictionary definitions for a (3 of 11)
(usually linked to the preceding noun) an informal form of of sorta sad; a kinda waste
British Dictionary definitions for a (4 of 11)
are(s) (metric measure of land)
chess See algebraic notation
British Dictionary definitions for a (5 of 11)
the first letter and first vowel of the modern English alphabet
any of several speech sounds represented by this letter, in English as in take, bag, calm, shortage, or cobra
Also called: alpha the first in a series, esp the highest grade or mark, as in an examination
from A to Z from start to finish, thoroughly and in detail
British Dictionary definitions for a' (6 of 11)
Scot variants of all
British Dictionary definitions for A (7 of 11)
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
a human blood type of the ABO group, containing the A antigen
(in Britain) a major arterial road: the A3 runs from London to Portsmouth
(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
the number 10 in hexadecimal notation
chem argon (now superseded by Ar)
Also: at ampere-turn
(in circuit diagrams) ammeter
(in combination) atomic: an A-bomb; an A-plant
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
Austria (international car registration)
British Dictionary definitions for a- (8 of 11)
not; without; opposite to: atonal; asocial
British Dictionary definitions for a- (9 of 11)
on; in; towards: afoot; abed; aground; aback
literary, or archaic (used before a present participle) in the act or process of: come a-running; go a-hunting
in the condition or state of: afloat; alive; asleep
British Dictionary definitions for Å (10 of 11)
British Dictionary definitions for A. (11 of 11)
acre(s) or acreage
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)
Abbreviation of adenine, ampere, angstrom, area
Scientific definitions for a- (2 of 3)
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)
Abbreviation of angstrom
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.