a
1 Americanindefinite article
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not any particular or certain one of a class or group.
a man; a chemical; a house.
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a certain; a particular.
one at a time; two of a kind; A Miss Johnson called.
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another; one typically resembling.
a Cicero in eloquence; a Jonah.
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one (used before plural nouns that are preceded by a quantifier singular in form): a hundred men (comparehundreds of men ); a dozen times (comparedozens of times ).
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indefinitely or nonspecifically (used with adjectives expressing number).
a great many years; a few stars.
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one (used before a noun expressing quantity).
a yard of ribbon; a score of times.
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any; a single.
not a one.
noun
PLURAL
A's, As, a's, as.-
the first letter of the English alphabet, a vowel.
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any spoken sound represented by the letter A or a, as in bake, hat, father, or small.
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something having the shape of an A .
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a written or printed representation of the letter A or a.
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a device, as a printer's type, for reproducing the letter A or a.
idioms
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not know from A to B, to know nothing; be ignorant.
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from A to Z, from beginning to end; thoroughly; completely.
He knows the Bible from A to Z.
abbreviation
abbreviation
preposition
abbreviation
abbreviation
preposition
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the first in order or in a series.
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Sometimes a
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(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.
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(in some school systems) a symbol designating the first semester of a school year.
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Music.
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the sixth tone in the scale of C major or the first tone in the relative minor scale, A minor.
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a string, key, or pipe tuned to this tone.
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a written or printed note representing this tone.
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(in the fixed system of solmization) the sixth tone of the scale of C major, called la.
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the tonality having A as the tonic note.
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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.
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Sometimes a the medieval Roman numeral for 50 or 500.
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Chemistry. (formerly) argon.
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Chemistry, Physics. mass number.
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Biochemistry.
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Logic. Also a universal affirmative.
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British. a designation for a motion picture recommended as suitable for adults.
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a proportional shoe width size, narrower than B and wider than AA.
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a proportional brassiere cup size, smaller than B and larger than AA.
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a quality rating for a corporate or municipal bond, lower than AA and higher than BBB.
abbreviation
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about.
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acre; acres.
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active.
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adjective.
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alto.
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ampere; amperes.
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anonymous.
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answer.
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are; ares.
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Baseball. assist; assists.
abbreviation
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Absolute.
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Academy.
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acre; acres.
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America.
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American.
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angstrom.
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answer.
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April.
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Artillery.
auxiliary verb
abbreviation
adjective
symbol
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music
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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
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a key, string, or pipe producing this note
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the major or minor key having this note as its tonic
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a human blood type of the ABO group, containing the A antigen
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(in Britain) a major arterial road
the A3 runs from London to Portsmouth
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a film certified for viewing by anyone, but which contains material that some parents may not wish their children to see
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( as modifier )
an A film
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mass number
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the number 10 in hexadecimal notation
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cards ace
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chem argon (now superseded by Ar )
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ampere(s)
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Also: at. ampere-turn
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absolute (temperature)
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(in circuit diagrams) ammeter
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area
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(in combination) atomic
an A-bomb
an A-plant
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chem affinity
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biochem adenine
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logic a universal affirmative categorical proposition, such as all men are mortal: often symbolized as SaP Compare E I 2 O 1
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a person whose job is in top management, or who holds a senior administrative or professional position
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( as modifier ) See also occupation groupings
an A worker
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abbreviation
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012determiner
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used preceding a singular countable noun, if the noun is not previously specified or known
a dog
a terrible disappointment
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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
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used preceding a noun or determiner of quantity
a cupful
a dozen eggs
a great many
to read a lot
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used preceding a noun indicating a concrete or abstract thing capable of being divided
half a loaf
a quarter of a minute
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each or every; per
once a day
fifty pence a pound
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a certain; one
to change policy at a stroke
a Mr Jones called
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(preceded by not) any at all
not a hope
symbol
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acceleration
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are(s) (metric measure of land)
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atto-
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chess See algebraic notation
noun
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the first letter and first vowel of the modern English alphabet
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any of several speech sounds represented by this letter, in English as in take, bag, calm, shortage, or cobra
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Also called: alpha. the first in a series, esp the highest grade or mark, as in an examination
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from start to finish, thoroughly and in detail
abbreviation
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acre(s) or acreage
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America(n)
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answer
prefix
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on; in; towards
afoot
abed
aground
aback
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literary (used before a present participle) in the act or process of
come a-running
go a-hunting
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in the condition or state of
afloat
alive
asleep
symbol
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012prefix
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012verb
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012preposition
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012determiner
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012Grammar
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.
Etymology
Origin of a1
First recorded in 1200–50; Middle English; originally preconsonantal phonetic variant of an 1
Origin of a-3
Middle English, late Old English; a 2, nowadays
Origin of a.5
< Latin annō, ablative of annus
Origin of A.6
< Latin annō, ablative of annus
Origin of a7
Originally Middle English a, preconsonantal variant of on ( a- 1 ); confused with a 1
Origin of a-9
Middle English; a 3
Origin of a.11
From the Latin word ante
Origin of A.12
From the Latin word ante
Origin of a13
Middle English; unstressed preconsonantal variant of of 1
Origin of a-15
Middle English; Old English a- (unstressed), ǣ-, ā-, ō- (stressed; abb, woof 1, oakum ), rarely or- ( 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
Origin of -a16
From Latin feminine ending -a, as Claudia, feminine of Claudius; -a 2
Origin of a19
First recorded in 1300–50; Middle English; a phonetic variant of have
Origin of a-20
Middle English < Latin ā-, a- (variant of ab- ab- ); in some words < French a- < Latin ab-, as in abridge
Origin of -a21
Probably generalized from the -a of magnesia
Origin of a22
First recorded in 1200–50; Middle English a, ha
Origin of a-23
Middle English, in some words < Middle French a- < Latin ad- prefix or ad preposition ( ad- ), as in abut; in others < Latin a- (variant of ad- ad- ), as in ascend
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.