Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The first letter of the modern English alphabet.
  • n. Any of the speech sounds represented by the letter a.
  • n. The first in a series.
  • n. Something shaped like the letter A.
  • n. The best or highest in quality or rank: grade A milk.
  • n. Music The sixth tone in the scale of C major or the first tone in the relative minor scale.
  • n. Music A key or scale in which A is the tonic.
  • n. Music A written or printed note representing this tone.
  • n. Music A string, key, or pipe tuned to the pitch of this tone.
  • n. 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.
  • idiom from A to Z Completely; thoroughly.
  • 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.
  • Used before a proper name to denote a type or a member of a class: the wisdom of a Socrates.
  • 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.
  • prep. In every; to each; per: once a month; one dollar a pound.
  • auxiliary v. Informal Have: He'd a come if he could.
  • abbr. acceleration
  • abbr. are (measurement)

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • Used in conjunction with the adjectives score, dozen, hundred, thousand, and million, as a function word.
  • Used before plural nouns modified by few, good many, couple, great many, etc.
  • n. The first letter of the basic modern Latin alphabet.
  • n. Used in the International Phonetic Alphabet and in several romanization systems of non-Latin scripts to represent an open front unrounded vowel.
  • n. atto-, the prefix for 10-18 in the International System of Units.
  • n. A year in SI Units, specifically a Julian year or exactly 365.25 days.
  • n. An are, a unit of area of which 100 comprise a hectare; ares.
  • n. The first letter of the English alphabet, called a and written in the Latin script.
  • n. The ordinal number first, derived from this letter of the English alphabet, called a and written in the Latin script.
  • n. The name of the Latin script letter A/a.
  • n. this sense?) A spoken sound represented by the letter a or A, as in map, mall, or male.
  • n. this sense?) A written representation of the letter A or a.
  • n. this sense?) A printer's type or stamp used to reproduce the letter a.
  • n. this sense?) An item having the shape of the letter a or A.
  • n. this sense?) (algebra) The first quantity, especially a constant, in an equation.
  • n. Distance from leading edge to aerodynamic center.
  • n. specific absorption coefficient
  • n. specific rotation
  • n. allele (recessive)
  • interj. A meaningless syllable; ah.
  • prep. Of.

from the GNU version of the Collaborative International Dictionary of English

  • 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 Phœnician 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 ä sound, the Phœnician alphabet having no vowel symbols.
  • 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♯) is the name of a musical tone intermediate between A and B. -- A flat (A♭) is the name of a tone intermediate between A and G.
  • An adjective, commonly called the indefinite article, and signifying one or any, but less emphatically.
  • In each; to or for each
  • Of.
  • A barbarous corruption of have, of he, and sometimes of it and of they.
  • An expletive, void of sense, to fill up the meter.
  • n.
  • prep. In; on; at; by.
  • prep. 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.

from The Century Dictionary and Cyclopedia

  • The first letter in the English alphabet, as also generally in the other alphabets which, like the English, come ultimately from the Phenician.
  • As a symbol, a denotes the first of an actual or possible series. Specifically
  • In music, the name of the sixth note of the natural diatonic scale of C, or the first note of the relative minor scale; the la of Italian, French, and Spanish musicians.
  • In the mnemonic words of logic, the universal affirmative proposition, as, all men are mortal.
  • In mathematics: In algebra, a, b, c, etc., the first letters of the alphabet, stand for known quantities, while x, y, z, the last letters, stand for unknown quantities; in geometry, A, B, C, etc., are used to name points, lines, and figures.
  • In abstract reasoning, suppositions, etc., A, B, C, etc., denote each a particular person or thing in relation to the others of a series or group.
  • In writing and printing, a, b, c, etc., are used instead of or in addition to the Arabic figures in marking paragraphs or other divisions, or in making references.
  • In naut. lang., A1, A2, etc., are symbols used in the Record of American and Foreign Shipping, and in Lloyd's Register of British and Foreign Shipping, to denote the relative rating of merchant vessels.
  • As an abbreviation, a stands, according to context, for acre, acting, adjective, answer, are (in the metric system), argent (in heraldry), anal (anal fin, in ichthyology), anechinoplacid (in echinoderms), etc.; in com., for approved, for accepted, and for Latin ad (commonly written @), “at” or “to”: as, 500 shares L. I. preferred @ 67½; 25 @ 30 cents per yard.
  • Attrib., having the form of the capital A, as a tent.
  • The form of an used before consonants and words beginning with a consonant-sound: as, a man, a woman, a year, a union, a eulogy, a oneness, a hope. An, however, was formerly often used before the sounds of h and initial long u and eu even in accented syllables (as, an hospital, an union), and is still retained by some before those sounds in unaccented syllables (as, an historian, an united whole, an euphonious sound).
  • A reduced form of the preposition on, formerly common in all the uses of on, but now restricted to certain constructions in which the preposition is more or less disguised, being usually written as one word with the following noun.
  • Of place: On, in, upon, unto, into; the preposition and the following noun being usually written as one word, sometimes with, but commonly without, a hyphen, and regarded as an adverb or a predicate adjective, but best treated as a prepositional phrase. Similarly
  • Of state: On, in, etc.: as, to be alive
  • to be asleep
  • to set afire; to be afloat; to set adrift.
  • Of time: On, in, at, by, etc., remaining in some colloquial expressions: as, to stay out a nights (often written o' nights); to go fishing a Sunday; now a days (generally written nowadays). , ,
  • Of process: In course of, with a verbal noun in -ing, taken passively: as, the house is a building; “while the ark was a preparing”(1 Pet. iii. 20); while these things were a doing. The prepositional use is clearly seen in the alternative construction with in: as, “Forty and six years was this temple in building,” John ii. 20.
  • Of action: In, to, into; with a verbal noun in -ing, taken actively.
  • A reduced form of of, now generally written o', as in man-o'-war, six o'clock, etc.
  • A modern provincial corruption of the pronoun I.
  • An old (and modern provincial) corruption of all genders and both numbers of the third personal pronoun, he, she, it, they. So quotha, that is, quoth he.
  • An old (and modern provincial) corruption of have as an auxiliary verb, unaccented, and formerly also as a principal verb.
  • All.
  • The early form of ah, preserved, archaically, before a leader's or chieftain's name, as a war-cry (but now treated and pronounced as the indefinite article).
  • A Latin preposition, meaning of, off, away from, etc.
  • A prefix or an initial and generally inseparable particle. It is a relic of various Teutonic and classical particles, as follows:
  • An unaccented inseparable prefix of verbs, and of nouns and adjectives thence derived, originally implying motion away, but in earlier English merely intensive, or, as in modern English, without assignable force, as in abide, abode, arise, awake, ago = agone, etc.
  • An apparent prefix, properly a preposition, the same as a, preposition
  • A prefix, being a reduced form of Anglo-Saxon of, prep., English off, from, as in adown (which see), or of later English of, as in anew, afresh, akin, etc. (which see).
  • A prefix, being a reduced form of Anglo-Saxon of-, an intensive prefix, as in athirst, ahungered (which see).
  • A prefix, being a reduced form of and- (which see), as in along (which see).
  • A prefix, being one of the reduced forms of the Anglo-Saxon prefix ge- (see i-), as in along
  • aware
  • aford, now spelled afford, simulating the Latin prefix af-
  • among
  • etc. The same prefix is otherwise spelled in enough, iwis, yclept, etc.
  • A prefix, being a reduced form of at-, mixed with a- for on-, in afore (which see).
  • A prefix, in ado, originally at do, northern English infinitive, equivalent to English to do. See ado.
  • A quasi-prefix, a mere opening syllable, in the interjections aha, ahoy. In aha, and as well in ahoy, it may be considered as ah.
  • A quasi-prefix, a mere opening syllable, in avast, where a-, however, represents historically Dutch houd in the original Dutch expression houd vast = English hold fast.
  • A prefix, being a reduced form of the Latin prefix ad-. , ,
  • A prefix, being a reduced form (in Latin, and so in English, etc.) of the Latin prefix ad- before sc-, sp-, st-, and gn-, as in ascend, aspire, aspect, astringent, agnate, etc.
  • A prefix, being a reduced form (in Middle English, etc.) of Latin ab-, as in abate (which see). In a few verbs this a- has taken a Latin semblance, as in abs-tain (treated as ab-stain), as-soil. See these words.
  • A prefix, being a reduced form (in Latin, and so in English, etc.) of the Latin prefix ab-, from, as in avert (which see).
  • A prefix, being an altered form of e-, reduced form of Latin ex-, as in amend, abash, etc., aforce, afray (now afforce, affray), etc. (which see).
  • A prefix, being a reduced form of an- for en-, in some words now obsolete or spelled in semblance of the Latin, or restored, as in acloy, acumber, apair, etc., later accloy, accumber, modern encumber, impair, etc.
  • A quasi-prefix, representing original Latin ah, interj., in alas (which see).
  • A prefix of Greek origin, called alpha privative, the same as English un-, meaning not, without, -less, used not only in words taken directly or through Latin from the Greek, as abyss, adamant, acatalectic, etc., but also as a naturalized English prefix in new formations, as achromatic, asexual, etc., especially in scientific terms, English or New Latin, as Apteryx, Asiphonata, etc.
  • A prefix of Greek origin, occurring unfelt in English acolyte, adelphous, etc.
  • A prefix of Greek origin, occurring unfelt in atlas, amaurosis, etc.
  • A prefix of Arabic origin, occurring unfelt in apricot, azimuth, hazard (for *azard), etc., commonly in the full form al-. See al-.
  • A suffix characteristic of feminine nouns and adjectives of Greek or Latin origin or semblance, many of which have been adopted in English without change. ; ; ; ;
  • A suffix, the nominative neuter plural ending of nouns and adjectives of the second and third declensions in Greek or Latin, some of which have been adopted in English without change of ending. ;
  • An unmeaning syllable, used in old ballads and songs to fill out a line.
  • . In music, the A next above middle C has (at French pitch) 435 vibrations per second. In medieval music, the final of the Æolian and hypoæolian modes.
  • In chem., the symbol for argon.
  • Also an abbreviation of ampere and of A-level (which see).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
  • n. the basic unit of electric current adopted under the Systeme International d'Unites
  • n. the blood group whose red cells carry the A antigen
  • n. one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
  • n. any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes
  • n. a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
  • n. the 1st letter of the Roman alphabet

Etymologies

Middle English, variant of an, an; see an1.
Middle English, from Old English an, in; see on.
Middle English, alteration of haven, to have; see have.
(American Heritage® Dictionary of the English Language, Fourth Edition)
Modification of capital letter A, from Latin A, from Ancient Greek letter Α (A). (Wiktionary)
Abbreviation of atto-, from Danish and Norwegian atten ("eighteen"). (Wiktionary)
From Latin annus (Wiktionary)
Abbreviation (Wiktionary)
Middle English, from Old English ān ("one, a, lone, sole"). The "n" was gradually lost before consonants in almost all dialects by the 15th century. (Wiktionary)
From Middle English a, ha contraction of have, or haven (Wiktionary)
Variant spelling of ah. (Wiktionary)
From Middle English, contraction of of. (Wiktionary)
From Middle English (Northern dialect) aw, alteration of all. (Wiktionary)
Symbols (Wiktionary)

Examples

  • Not that it makes it any better, but I'm pretty sure the 'big a*& cake' is a riff on a chain a prominent rapper wore, with a medallion that had ' big a#$ chain'.

    Tell Me What You Want, What You Really Really Want

  • So, having argued for a second root for sit that was *es- (which they relate to Sanskrit a:s-, Avestan a:s-/a:h-, Hittite eš-, and Greek he:stai 'sits'), they then suggest a connection to Hurrian ašš- and Urartean aš-, which then suggests a connection to Proto-Uralic *ase- (there should be an acute accent over the s)

    languagehat.com: EYAS.

  • For this reason the tube, TT ', is provided with a notch opposite the piece _a m l_, and the two arms, _a_ and _m_, of the latter are shaped like a V, as may be seen in part in the plan in Fig. 2.

    Scientific American Supplement, No. 362, December 9, 1882

  • "Good gracious," said he, "she has the voice of a----" (words failed him, in his astonishment) "the voice of a-- a monster!"

    The French Immortals Series — Complete

  • The receiver consists of a closed box, K, in the interior of which there is a very intense source of light whose rays escape by passing through apertures, _a a'_, in the front part

    Scientific American Supplement, No. 508, September 26, 1885

  • Mr. Tennyson (though he, too, would, as far as his true love is concerned, not unwillingly 'be an earring,' 'a girdle, 'and 'a necklace,' p. 45) in the more serious and solemn exordium of his works ambitions a bolder metamorphosis -- he wishes to be -- _a river_!

    Early Reviews of English Poets

  • As an example of the use of the cross to denote a square, we have Figure 124, which represents a piece having a hexagon head, section _a_, _a'_, that is rectangular, a collar _b_, a square part _c_, and a round stem _d_.

    Mechanical Drawing Self-Taught

  • She went away right in the midst of a-- of a difference of opinion we were having; she didn't even let me know she was going, and never wrote a line to me, and then came back telling everybody she'd had 'a perfectly gorgeous time! '

    The Magnificent Ambersons; illustrated by Arthur William Brown

  • "Because pretty near all he had on was a towel an 'a-- a sort of a---- immodes' britch-cloth," explained Guy Little confidentially.

    Man to Man

  • He's a-- a cross between a Republican mule and a party-bolting boa-constrictor, an 'a hybrid like that hasn't got any place in nature.

    Slippy McGee, Sometimes Known as the Butterfly Man

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  • "In the mnemonic words of logic, the universal affirmative proposition, as, all men are mortal. Similarly, I stands for the particular affirmative, as, some men are mortal; E for the universal negative, as, no men are mortal; O for the particular negative, as, some men are not mortal. The use of these symbols dates from the thirteenth century; they appear to be arbitrary applications of the vowels a, e, i, o, but are usually supposed to have been taken from the Latin AffIrmo, I affirm, and nEgO, I deny. But some authorities maintain that their use in Greek is much older."

    --CD&C

    February 14, 2013