a (1)
indefinite article, form of an used before consonants, mid-12c., a weakened form of Old English an "one" (see an). The disappearance of the -n- before consonants was mostly complete by mid-14c. After c. 1600 the -n- also began to vanish before words beginning with a sounded -h-; it still is retained by many writers before unaccented syllables in h- or (e)u- but is now no longer normally spoken as such. The -n- also lingered (especially in southern England dialect) before -w- and -y- through 15c.

It also is used before nouns of singular number and a few plural nouns when few or great many is interposed.
a (2)
as in twice a day, etc., a reduced form of Old English an "on" (see on (prep.)), in this case "on each." The sense was extended from time to measure, price, place, etc. The habit of tacking a onto a gerund (as in a-hunting we will go) was archaic after 18c.
A
first letter of the Roman alphabet, based on Greek alpha (see alpha). In music from c. 1600 as the name of the sixth note of the natural scale; it is the note given by a fixed-tone instrument (usually oboe or organ) to which all the instruments of an orchestra are tuned. As a blood type, 1926, denoting A agglutinogens. The A side of a two-sided record (by 1962, see side (n.)) held the material chosen for promotion. A-bomb, short for atom bomb, was in newspaper headlines by Aug. 8, 1945.
a capella
1876, earlier alla capella (1824), from Italian, "in the style of Church music, in the manner of the chapel," literally "according to the chapel," from cappella "chapel" (see chapel). Originally in reference to older church music (pre-1600) which was written for unaccompanied voices; applied 20c. to unaccompanied vocal music generally. Italian a is from Latin ad "to, toward; for; according to" (see ad-); alla is a la "to the."
a deux
French, à deux, literally "for two," from à, from Latin ad "to, toward; for" (see ad-) + deux (see deuce). By 1876 as a French term in English.
a la
from French à la, literally "to the," hence "in the manner of, according to," from à, from Latin ad "to" (see ad-) + la, fem. of definite article le "the," from Latin ille (fem. illa; see le). Attested in English in French terms from fashion or cookery since late 16c.; since c. 1800 used in native formations with English words or names.
a la carte
"ordered by separate items" (itemized on a bill); distinguished from a table d'hôte, indicating a meal served at a fixed, inclusive price; 1826, from French à la carte, literally "by the card" (see a la + card (n.1)).
a la mode (adv.)
also alamode, 1640s, from French à la mode (15c.), literally "in the (prevailing) fashion" (see a la + mode (n.2)). In 17c., sometimes nativized as all-a-mode. Cookery sense in reference to a dessert served with ice cream is 1903, American English; earlier it was used of a kind of beef stew or soup (1753).
a posteriori
17c., in reference to reasoning from a consequent to its antecedent, from an effect to its cause; Latin, literally "from what comes after;" from a "off, away from," usual form of ab before consonants (see ab-) + posteriori, neuter ablative of posterius, comparative of posterus "after, subsequent," from post "after" (see post-). Opposed to a priori. In modern use (from c. 1830, based on Kant) roughly equivalent to "from experience."
a priori
1710, "from cause to effect," a Latin term in logic from c. 1300, in reference to reasoning from antecedent to consequent, based on causes and first principles, literally "from what comes first," from priori, ablative of prior "first" (see prior (adj.)). Opposed to a posteriori. Since c. 1840, based on Kant, used more loosely for "cognitions which, though they may come to us in experience, have their origin in the nature of the mind, and are independent of experience" [Century Dictionary]. Related: Apriorist; apriorism; aprioristic. The a is the usual form of Latin ab "off, of, away from" before consonants (see ab-).
A&P
original U.S. grocery chain and leading food retailer of the mid-20c., the abbreviation by 1875, originally The Great Atlantic and Pacific Tea Company, which grew out of a New York firm founded 1859 by George Gilman and subsequently expanded by George Huntington Hartford. It ceased operation in 2015.
a- (2)
word-forming element meaning "away," from Latin a "off, of, away from," the usual form of Latin ab before consonants (see ab-). As in avert, avocation. It is also the a in a priori and the à in Thomas à Kempis.
a- (1)
prefix or inseparable particle, a relic of various Germanic and Latin elements.

In words derived from Old English, it commonly represents Old English an "on" (see on (prep.)), as in alive, above, asleep, aback, abroad, afoot, ashore, ahead, abed, aside, etc., forming adjectives and adverbs from nouns, with the notion "in, at; engaged in." In this use it is identical to a (2).

It also can represent Middle English of (prep.) "off, from," as in anew, afresh, akin, abreast. Or it can be a reduced form of the Old English past participle prefix ge-, as in aware.

Or it can be the Old English intensive a-, originally ar- (cognate with German er- and probably implying originally "motion away from"), as in abide, arise, awake, ashamed, marking a verb as momentary, a single event. Such words sometimes were refashioned in early modern English as though the prefix were Latin (accursed, allay, affright are examples).

In words from Romanic languages, often it represents reduced forms of Latin ad "to, toward; for" (see ad-), or ab "from, away, off" (see ab-); both of which by about 7c. had been reduced to a in the ancestor of Old French. In a few cases it represents Latin ex.
[I]t naturally happened that all these a- prefixes were at length confusedly lumped together in idea, and the resultant a- looked upon as vaguely intensive, rhetorical, euphonic, or even archaic, and wholly otiose. [OED]
a- (3)
prefix meaning "not, without," from Greek a-, an- "not" (the "alpha privative"), from PIE root *ne- "not" (source also of English un-).

In words from Greek, such as abysmal, adamant, amethyst; also partly nativized as a prefix of negation (asexual, amoral, agnostic). The ancient alpha privatum, denoting want or absence.

Greek also had an alpha copulativum, a- or ha-, expressing union or likeness, which is the a- expressing "together" in acolyte, acoustic, Adelphi, etc. It is from PIE root *sem- (1) "one; as one, together with."
A-1
also A1, A-one, "first-rate," 1837 (in Dickens); a figurative use from Lloyd's of London marine insurance company's system for selective rating of merchant vessels ("Register of British and Foreign Shipping"), where it is the designation for ships in first-class condition. The letter refers to the condition of the hull of the ship itself, and the number rating to the equipment. Also used in equivalent ratings in U.S., where colloquially it is sometimes expanded to A No. 1.
A-frame
type of framework shaped like the capital letter "A," 1909; as a type of building construction in this shape from 1932.
A-line (adj.)
descriptive of a dress or skirt flared in shape of a capital letter "A," 1955, in reference to the creations of French fashion designer Christian Dior (1905-1957).
A-list (adj.)
in celebrity sense, 1984, from A in the sense of "first, best" (as in A-1) + list (n.1).
A-OK
1961, said to be an abbreviation of all (systems) OK; popularized in the jargon of U.S. astronauts. See OK.
A.A.
also AA, abbreviation of Alcoholics Anonymous, attested by 1941, American English. The group name was the title of a book published in 1938 by the founder, Bill W. From 1914 as an abbreviation of anti-aircraft guns.
A.A.A.
also AAA, abbreviation of American Automobile Association, attested 1902, American English, the year the organization was founded.
A.B.
affixed to a name, abbreviation of Modern Latin Artium Baccalaureus "Bachelor of Arts" (see bachelor), 1773, American English. British English preferred B.A.. A.B. was used in Britain to mean able-bodied on seamen's papers.
A.D.
1570s, an abbreviation of Latin Anno Domini "Year of the Lord." This system of counting years was put forth by Dionysius Exiguus in 527 or 533 C.E., but used at first only for Church business. Introduced in Italy in 7c., France (partially) in 8c. In England, first found in a charter of 680 C.E. Ordained for all ecclesiastical documents in England by the Council of Chelsea, July 27, 816.

The resistance to it might have come in part because Dionysius chose 754 A.U.C. as the birth year of Jesus, while many early Christians would have thought it was 750 A.U.C. (See John J. Bond, "Handy-Book of Rules and Tables for Verifying Dates With the Christian Era," 4th ed., London: George Bell & Sons, 1889.) There is a use of simple a for anno domini in an English document from c. 1400; A.C., for Anno Christi, also was common 17c.
A.H.
in Islamic calendrical reckoning, 1788, abbreviation of Medieval Latin Anno Hegirae, "Year of the Hegira," the flight of Muhammad from Mecca in 622 C.E., from which Muslims reckon time; from ablative of annus "year" (see annual (adj.)) + genitive of hegira.
a.k.a.
also a k a, aka, initialism (acronym) for also known as; attested in legal documents by 1936.
a.m.
also a.m., 1762 in reference to hours, an abbreviation of Latin ante meridiem "before noon" (q.v.). Synonymous with "morning" by 1776. AM as a type of radio wave broadcast, 1921, abbreviation of amplitude modulation (see amplitude). Affixed to a name, an abbreviation of artium magister "Master of Arts," an abbreviation preferable in a purely Latin idiom; British English prefered M.A. In some old chronologies, a.m. is anno mundi "year of the world."
A.P.R.
also APR, abbreviation of annual percentage rate, attested from 1979, American English.
a.s.a.p.
also asap, adverbial phrase pronounced either as a word (acronym) or as four letters (initialism), 1955, from initial letters of phrase as soon as possible; originally U.S. Army jargon.
A.U.C.
as an abbreviation in Roman history in reckoning of dates it represent either ab urbe condita (q.v.) "from the founding of the city" or Anno Urbis Conditae "in the year of the founded city," from ablative of annus "year" (see annual (adj.)) + genitive of urbs "city" (see urban) + genitive of condita, fem. of conditus, past participle of condere "to set up, put together" (see abscond)
A.V.
abbreviation of Authorized Version (of the English Bible, 1611) attested from 1868; see authorize.
aardvark (n.)
also aard-vark, South African groundhog, 1833 (in German from 1824), from Afrikaans Dutch aardvark, literally "earth-pig" (it burrows), from aard "earth," from Proto-Germanic *ertho- (see earth (n.)) + vark "pig," from Middle Dutch varken "small pig," which is from Proto-Germanic *farhaz (source also of Old High German farah, German Ferkel "young pig, sucking pig," a diminutive form; Old English fearh), from PIE root *porko- "young pig."
aardwolf (n.)
also aard-wolf, 1833, from Afrikaans Dutch aardwolf, literally "earth-wolf," from aard "earth" (see earth (n.)) + wolf "wolf" (see wolf (n.)).
Aaron
masc. proper name, in the Old Testament the brother of Moses, from Hebrew Aharon, which is said to be probably of Egyptian origin. The Arabic form is Harun. Related: Aaronic. Aaron's beard as a popular name for various plants (including St. John's wort and a kind of dwarf evergreen) deemed to look hairy in some way is from 1540s. Aaron's rod is from 1834 in botany, 1849 in ornamentation; the reference is biblical (Exodus vii.19, etc.).
ab initio
c. 1600, Latin, literally "from the beginning," from ab "from" (see ab-) + ablative of initium "entrance, beginning," which is from or related to the verb inire "to go into, enter upon, begin" (see initial).
ab ovo
"from the beginning," Latin, literally "from the egg," from ab "from, away from" (see ab-) + ablative of ovum "egg" (see ovum). The expression is said to refer to the Roman custom of beginning the meal with eggs, as also in the expression ab ovo usque ad mala, "from the egg to the apples" (Horace), hence "from the beginning to the end" (compare early 20c. soup to nuts).
ab urbe condita
with year-dates, an occasional Roman method of identifying a given year by reference to the time passed since founding of the city, which in 1c. B.C.E. was calculated to have taken place in what we would call 753 B.C.E. Literally "from the city founded;" the elements are ab "from" (see ab-) + ablative of urbs "city" (see urban) + fem. past participle of condere "put together, store," from assimilated form of com- "together" (see com-) + -dere "put," from PIE root *dhe- "to put, place."
ab-
word-forming element meaning "away, from, from off, down," denoting disjunction, separation, departure; from Latin ab (prep.) "off, away from" in reference to space or distance, also of time, from PIE root *apo- "off, away" (also the source of Greek apo "off, away from, from," Sanskrit apa "away from," Gothic af, English of, off; see apo-).

The Latin word also denoted "agency by; source, origin; relation to, in consequence of." Since classical times usually reduced to a- before -m-, -p-, or -v-; typically abs- before -c-, -q-, or -t-.
aba (n.)
outer garment of coarse, woolen stuff, of a type worn in Arabia and Syria, 1811, from Arabic. Also of the cloth it is made from (often goat or camel hair).
aback (adv.)
c. 1200, a contraction of Old English on bæc "backward, behind, at or on the back;" see see a- (1) + back (n.). Now surviving mainly in taken aback, originally a nautical expression in reference to a vessel's square sails when a sudden change of wind flattens them back against the masts and stops the forward motion (1754). The figurative sense from this, "suddenly or unexpectedly checked or disappointed," is by 1792.
abacus (n.)
late 14c., "sand table for drawing, calculating, etc.," also "art of calculating with an abacus," from Latin abacus, from Greek abax (genitive abakos) "counting table, board for drawing," of uncertain etymology. It is said to be from a Semitic source, Phoenician or Hebrew abaq "sand strewn on a surface for writing," literally "dust," from the Semitic root a-b-q "to fly off," but Beekes and others find this "semantically weak."

Originally a drawing board covered with dust or sand on which mathematical equations or calculations could be traced and erased. In reference to the other type of abacus, a counting frame with beads or balls strung on wires or rods, it is attested from 17c. or later in English. Both types were known in antiquity across Eurasia. Related: Abacist (late 14c.)
Abaddon
late 14c., used in Revelations ix.11 of "the angel of the bottomless pit," and by Milton of the pit itself, from Hebrew Abhaddon, literally "destruction," from abhadh "he perished." The Greek form was Apollyon.
abaft (adv.)
"in or farther toward the back part (of a ship)," as opposed to forward, 1590s, from Middle English on baft (late 13c.) "back, behind, to the rear," from Old English on bæftan. For first element, see a- (1). The second component is itself a compound of be "by" (see by) and æftan "aft" (see aft). The word has been saved by the sailors (the stern being the "after" part of a vessel), the rest of the language having left it in Middle English.
abalienate (v.)
in civil law, "transfer title of ownership to another," 1550s, from Latin abalienatus, past participle of abalienare "to remove, separate, alienate, make formal transfer of," literally "to convey away," from ab "off, away from" (see ab-) + alienare "to separate" (from alius "another, other, different," from PIE root *al- (1) "beyond"). Related: Abalienated; abalienating.
abalienation (n.)
"act of transferring title of ownership," 1650s, from Latin abalienationem (nominative abalienatio), in law, "transfer of property, sale," noun of action from past participle stem of abalienare "to separate, transfer the ownership of," from ab "off, away from" (see ab-) + alienare "to separate" (from alius "another, other, different," from PIE root *al- (1) "beyond").
abalone (n.)
type of large mollusk found on the California coast, 1850, American English, from Spanish abulon, a loan-word from Rumsen (an extinct native language in the Costanoan family), aluan, said to mean "red abalone." Prized for its meat (once an important California export) and for the mother-of-pearl in its large shells (also called ear-shells).
abandon (v.)
late 14c., "to give up (something) absolutely, relinquish control, give over utterly;" also reflexively, "surrender (oneself), yield (oneself) utterly" (to religion, fornication, etc.), from Old French abandoner "surrender, release; give freely, permit," also reflexive, "devote (oneself)" (12c.).

The Old French word was formed from the adverbial phrase à bandon "at will, at discretion," from à "at, to" (from Latin ad; see ad-) + bandon "power, jurisdiction," from Latin bannum, "proclamation," which is from a Frankish or other Germanic word, from Proto-Germanic *bannan- "proclaim, summon, outlaw" (things all done by proclamation); see ban (v.).
Mettre sa forest à bandon was a feudal law phrase in the 13th cent. = mettre sa forêt à permission, i.e. to open it freely to any one for pasture or to cut wood in; hence the later sense of giving up one's rights for a time, letting go, leaving, abandoning. [Auguste Brachet, "An Etymological Dictionary of the French Language," transl. G.W. Kitchin, Oxford, 1878]
Meaning "to leave, desert, forsake (someone or something) in need" is from late 15c. (Etymologically, the word carries a sense of "put (something) under someone else's control.") Earliest appearance of the word in English is as an adverb (mid-13c.) with the sense "under (one's) control," hence also "unrestricted." Related: Abandoned; abandoning.
abandon (n.)
"a letting loose, freedom from self-restraint, surrender to natural impulses," by 1822 as a French word in English (it remained in italics or quotation marks through much of the 19c.; the naturalized abandonment in this sense was attempted from 1834), from a sense in French abandon "abandonment; permission" (12c.), from abandonner "to surrender, release" (see abandon (v.)).

The noun was borrowed earlier (c. 1400) from Old French in a sense "(someone's) control;" and compare Middle English adverbial phrase at abandon, i.e. "recklessly," attested from late 14c. In Old French, the past participle adjective abandoné came to mean "zealous, eager, unreserved."
abandoned (adj.)
"self-devoted" to some practice or purpose (usually evil), late 14c., past participle adjective from abandon (v.) in the reflexive sense. Hence, in a general way, "shamelessly wicked" (1690s). Meaning "deserted, forsaken" is from late 15c.
abandonment (n.)
1610s, "action of relinquishing to another," from French abandonnement (Old French abandonement), from abandonner "to give up" (see abandon (v.)). Meaning "a deserting, forsaking" (of one's family, principles, etc.) is by 1788; from 1839 as "condition of being forsaken." In law, the relinquishing of a title, privilege, or claim. In music, Italian abbandonatamente is the instruction to play so as to make the time subordinate to the feeling.
abase (v.)
late 14c., "reduce in rank, etc.," from Old French abaissier "diminish, make lower in value or status; lower oneself" (12c.), literally "bend, lean down," from Vulgar Latin *ad bassiare "bring lower," from ad "to, toward" (see ad-) + Late Latin bassus "low, short" (see base (adj.)).

The form in English was altered 16c. by influence of base (adj.), making the word an exception to the rule that Old French verbs with stem -iss- enter English as -ish (comprehension might have played a role; earlier forms of abase often are identical with those of abash). Literal sense of "lower, depress" (late 15c.) is archaic or obsolete. Related: Abased; abasing.