WordReference Random House Learner's Dictionary of American English © 2017
A, a /eɪ/USA pronunciation   n.[countable]pl.  A's or As, a's or as. 
  1. Linguisticsthe first letter of the English alphabet.
  2. Educationa school grade or mark indicating excellence:received an A in English.
Idioms
  1. Idioms from A to Z, completely;
    thoroughly:He knew the rules of the game from A to Z.


a1 /ə; when stressed eɪ/USA pronunciation   indefinite article. [usually before count nouns]
  1. one:a friend of mine; a month ago.
  2. (used to refer to the class of things the noun belongs to): A dog has four legs.
  3. (used to refer to a rate or measurement with the noun) per;
    each: My dentist charges $50 a filling.
  4. (used before words like little, lot, few):a little time; a few stars.
  5. (used before noncount nouns to indicate a single portion, container, unit, type, or instance of that noun): I'll have a coffee (= a cup of coffee) with sugar.
  6. (used before a proper name):
    • a certain;
      a particular: A Mr. Johnson called and wants you to call back.
    • a work of art by:The investor paid $5 million for a Van Gogh.

A,  Symbol.
  1. Music and Dance
    • in music, the sixth tone of the C major scale.
  2. Physiologya major blood group.

a-1  ,[prefix.]
  • a- is used before some nouns to make them into adverbs showing "place where'':a-  +  shore → ashore = on (or into) the shore.
  • a is also used before some verbs to make them into words showing a state or process:a- +  sleep → asleep (= sleeping);a- + blaze → ablaze (= blazing).

  • a-1  ,
  • [prefix.] a- is used before some adjectives to mean "not'': a- + moral → amoral (= without morals);
    a-
    + tonal → atonal (= without tone).

  • A.,  an abbreviation of:
    1. America.
    2. American.

    a.,  an abbreviation of:
    1. acre.
    2. active.
    3. Grammaradjective.
    4. Music and Dancealto.
    5. Electricityampere.
    6. answer.

    WordReference Random House Unabridged Dictionary of American English © 2017
    A, a  (ā),USA pronunciation n., pl.  A's  or As, a's  or as. 
    1. Linguisticsthe first letter of the English alphabet, a vowel.
    2. Linguisticsany spoken sound represented by the letter A or a, as in bake, hat, father, or small.
    3. something having the shape of anA.
    4. a written or printed representation of the letter A or a.
    5. Printinga device, as a printer's type, for reproducing the letter A or a.
    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.

    a1  (ə; when stressed ā),USA pronunciation  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, originally preconsonantal phonetic variant of an1 Middle English
      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.

    a2  (ə; when stressed ā),USA pronunciation prep. 
    1. Pronounseach;
      every;
      per:ten cents a sheet; three times a day.
    • confused with a1 origin, originally Middle English a, preconsonantal variant of on (see a-1)

    a3  (ə),USA pronunciation prep. 
    1. [Pron. Spelling.]a reduced, unstressed form of  of (often written as part of a single, unhyphenated word):cloth a gold; kinda;sorta.
    • unstressed preconsonantal variant of of1 Middle English

    a4  (ə),USA pronunciation  auxiliary verb.
    1. [Pron. 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.Cf. of2.
    • phonetic variant of have Middle English

    a5  (ə, a, ä),USA pronunciation pron. 
    1. [Brit. Dial.]
    2. British Termshe.
    3. British Termsshe.
    4. British Termsit.
    5. British Termsthey.
    6. British TermsI.
    • Middle English a, ha

    a'  (ä, ô),USA pronunciation adj. 
    1. Scottish Termsall:for a' that.
    Also,  a. 
    A  ,
  • Electricityampere;
    amperes.
  • Physics, Educationangstrom.
  • Educationanswer.
  • British Terms, Music and Dancearterial (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 l.c.) (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 l.c.) (in some school systems) a symbol designating the first semester of a school year.
    4. [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.
    5. Physiologya 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. Cf. ABO system.
    6. (sometimes l.c.) the medieval Roman numeral for 50 or 500. Cf. Roman numerals.
    7. Chemistry(formerly) argon.
    8. [Chem., Physics.]See  mass number. 
    9. Biochemistry
      • adenine.
      • alanine.
    10. Drugs, Philosophy[Logic.]See  universal affirmative. 
    11. British Terms, Show Businessa designation for a motion picture recommended as suitable for adults. Cf. AA (def. 5), U (def. 5), X (def. 9).
    12. Clothinga proportional shoe width size, narrower than B and wider than AA.
    13. Clothinga proportional brassiere cup size, smaller than B and larger than AA.
    14. Businessa quality rating for a corporate or municipal bond, lower than AA and higher than BBB.

    a  ,[Meas.]
    1. Philosophyare;
      ares.

    a  , Symbol, Logic.
    1. See  universal affirmative. 

    Å  , Symbol, Physics.
    1. angstrom.

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

  • a-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).
    • compare a2, nowadays Middle English, late Old English

    a-2  ,
  • a reduced form of the Old English preposition of: akin;
    afresh;
    anew.
    • see a3 Middle English

    a-3  ,
  • 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).
    • *ud-s, akin to out; in some cases confused with a-4, as in abridge
    • unstressed Indo-European *uss-
    • Middle English; Old English a- (unstressed), ǣ-, ā-, ō- (stressed; see abb, woof1, oakum), rarely or- (see ordeal) Gmc *uz-

    a-4  ,
  • var. of  ab- before p and v: aperient;
    avert.
    • Latin ab-, as in abridge
    • French a-
    • Latin ā-, a- (variant of ab- ab-); in some words
    • Middle English

    a-5  ,
  • 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.
    • Latin a- (variant of ad- ad-), as in ascend
    • Latin ad- prefix or ad preposition (see ad-), as in abut; in others
    • Middle French a-
    • Middle English, in some words

    a-6  ,
  • var. of  an- 1 before a consonant, meaning "not,'' "without'':amoral;atonal;achromatic.

  • -a1  ,
  • a plural ending of nouns borrowed from Greek and Latin:phenomena; data;errata;genera.

  • -a2  ,
  • 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.

  • -a3  ,
  • an ending of personal names forming feminines from masculines:Georgia; Roberta.
    • Latin feminine -a (see -a2), as Claudia, feminine of Claudius

    -a4  ,
  • a suffix designating the oxide of the chemical element denoted by the stem:alumina;ceria;thoria.
    • probably generalized from the -a of magnesia

    A.  ,
  • Absolute.
  • Academy.
  • Weights and Measuresacre;
    acres.
  • America.
  • American.
  • Weights and Measuresangstrom.
  • year.
    • Latin annō, ablative of annus
  • answer.
  • before.
    • Latin annō, ablative of annus
  • April.
  • MilitaryArtillery.

  • a.  ,
  • about.
  • acre;
    acres.
  • active.
  • Grammaradjective.
  • Music and Dancealto.
  • Electricityampere;
    amperes.
  • year.
    • Latin annō, ablative of annus
  • anonymous.
  • answer.
  • before.
    • Latin annō, ablative of annus
  • Weights and Measuresare;
    ares.
  • Sport[Baseball.]assist;
    assists.

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