ahistoric (adj.) Look up ahistoric at Dictionary.com
"not historical, lacking in historical background or justification," 1911, from a- (2) "not" + historic.
ahistorical (adj.) Look up ahistorical at Dictionary.com
"without reference to or regard for history, considering only contemporary situations," 1950, from a- (2) "not" + historical.
ahoy (interj.) Look up ahoy at Dictionary.com
also a hoy, 1751, from a (probably merely a preliminary sound) + hoy, a nautical call used in hauling. The original form of the greeting seems to have been ho, the ship ahoy!
Ahura Mazda Look up Ahura Mazda at Dictionary.com
from Avestan ahura- "spirit, lord," from Indo-Iranian *asuras, from suffixed form of PIE root *ansu- "spirit" (see Aesir) + Avestan mazda- "wise," from PIE *mens-dhe- "to set the mind," from root *men- (1) "to think" (see mind (n.)) + *dhe- "to put" (see factitious).
AI Look up AI at Dictionary.com
also a.i., by 1971, abbreviation of artificial intelligence.
aid (v.) Look up aid at Dictionary.com
"to assist, help," c. 1400, from Old French aidier "help, assist" (Modern French aider), from Latin adiutare, frequentative of adiuvare (past participle adiutus) "to give help to," from ad- "to" (see ad-) + iuvare "to help, assist, give strength, support, sustain," which is from a PIE source perhaps related to the root of iuvenis "young person" (see young (adj.)). Related: Aided; aiding.
aid (n.) Look up aid at Dictionary.com
early 15c., "war-time tax," also "help, support, assistance," from Old French aide, earlier aiudha "aid, help, assistance" (9c.), from Late Latin adiuta, noun use of fem. of adiutus, past participle of Latin adiuvare "to give help to," from ad "to" (see ad-) + iuvare "to help, give strength, support, sustain," which is from a PIE source perhaps related to the root of iuvenis "young person" (see young (adj.)). Meaning "thing by which assistance is given" is recorded from 1590s; meaning "person who assists, helper" is from 1560s. Meaning "material help given by one country to another" is from 1940.
aide (n.) Look up aide at Dictionary.com
"officer whose duty is to receive and communicate the orders of a general officer," 1777, short for aide-de-camp (1660s), a French term in English, literally "camp assistant" (see aid (n.)). Plural of the full term is aides-de-camp.
AIDS (n.) Look up AIDS at Dictionary.com
1982, acronym formed from acquired immune deficiency syndrome. AIDS cocktail attested by 1997, the thing itself said to have been in use from 1995.
aikido (n.) Look up aikido at Dictionary.com
Japanese art of self-defense, 1936, literally "way of adapting the spirit," from Japanese ai "together" (from au "to harmonize") + ki "spirit" + do "way, art," from Chinese tao "way."
ail (v.) Look up ail at Dictionary.com
c. 1300, from Old English eglan "to trouble, plague, afflict," from Proto-Germanic *azljaz (source also of Old English egle "hideous, loathsome, troublesome, painful;" Gothic agls "shameful, disgraceful," agliþa "distress, affliction, hardship," us-agljan "to oppress, afflict"), from PIE *agh-lo-, suffixed form of root *agh- (1) "to be depressed, be afraid." Related: Ailed; ailing; ails. From late Old English also of mental states and moods.
It is remarkable, that this word is never used but with some indefinite term, or the word no thing; as What ails him? ... Thus we never say, a fever ails him. [Johnson]
ailanthus (n.) Look up ailanthus at Dictionary.com
"tree of heaven," 1807, Modern Latin, from Amboyna (Malay) ailanto, said to mean "tree of the gods." The spelling was altered by influence of Greek anthos "flower" (for which see anther).
aileron (n.) Look up aileron at Dictionary.com
"hinged flap on the trailing edge of an airplane wing," 1909, from French aileron, diminutive of aile "wing," from Old French ele "wing" (12c.), from Latin ala "wing" (see aisle).
ailing (adj.) Look up ailing at Dictionary.com
"sick, ill, suffering," 1590s, present-participle adjective from ail (v.).
ailment (n.) Look up ailment at Dictionary.com
"sickness, disease, indisposition," 1706, from ail + -ment.
ailurophile (n.) Look up ailurophile at Dictionary.com
"cat lover," 1931, from Greek ailouros "cat," which is of unknown origin, + -phile.
ailurophobia (n.) Look up ailurophobia at Dictionary.com
"morbid fear of cats," 1905, from -phobia "fear" + Greek ailouros "cat," which is of unknown origin. Folk etymology connects it with aiolos "quick-moving" + oura "tail." Related: Ailurophobe (1914).
aim (v.) Look up aim at Dictionary.com
c. 1300, "to estimate (number or size), calculate, count" (senses now obsolete), from Old French aesmer, esmer (Old North French amer) "to value, rate; count, estimate," ultimately from Latin aestimare "appraise, determine the value of" (see esteem (v.)).

Meaning in English apparently developed from "calculate," to "calculate with a view to action, plan," then to "direct a missile, a blow, etc." (late 14c.). Also used in Middle English of directing a letter, planting an altar, pitching a tent. Intransitive sense "intend, attempt" (early 14c.) was used by Shakespeare but is now considered colloquial. Related: Aimed; aiming.
aim (n.) Look up aim at Dictionary.com
late 14c., "a purpose, thing intended;" from aim (v.) or from nouns from the verb in Old French. Meaning "action of aiming" is from early 15c. To take aim originally was make aim (early 15c.).
aimless (adj.) Look up aimless at Dictionary.com
"without aim or purpose," 1620s, from aim (n.) + -less. Related: Aimlessly; aimlessness.
ain't Look up ain't at Dictionary.com
1706, originally a contraction of am not, and considered proper as such until in early 19c. it began to be also a generic contraction of are not, is not, has not, etc. This was popularized in representations of London cockney dialect in Dickens, etc., which led to the word being banished entirely from correct English.
Ainu Look up Ainu at Dictionary.com
people native to northern Japan and far eastern Russia, 1819, from the Ainu self-designation, literally "man, human." Once considered to be Caucasian, based on their appearance; DNA testing has disproved this. Their language is an isolate with no known relatives.
aioli (n.) Look up aioli at Dictionary.com
garlic mayonnaise, 1914, from Provençal aioli, from ai (corresponding to French ail "garlic") + oli (corresponding to French huile) "oil," from Latin oleum (see oil (n.)).
air (n.1) Look up air at Dictionary.com
c. 1300, "invisible gases that make up the atmosphere," from Old French air "atmosphere, breeze, weather" (12c.), from Latin aer "air, lower atmosphere, sky," from Greek aer (genitive aeros) "air" (related to aenai "to blow, breathe"), which is of unknown origin.

It is possibly from a PIE *awer- and thus related to aeirein "to raise" and arteria "windpipe, artery" (see aorta) on notion of "lifting, that which rises." In Homer mostly "thick air, mist;" later "air" as one of the four elements. Words for "air" in Indo-European languages tend to be associated with wind, brightness, sky. In English, air replaced native lyft, luft (see loft (n.)).

In old chemistry, air (with a qualifying adjective) was used of any gas. To be in the air "in general awareness" is from 1875; up in the air "uncertain, doubtful" is from 1752. To build castles in the air is from 1590s (in 17c. English had airmonger "one preoccupied with visionary projects"). Broadcasting sense (as in on the air, airplay) first recorded 1927. To give (someone) the air "dismiss" is from 1900. Air pollution is attested by 1870. Air guitar by 1983. Air traffic controller is from 1956.
air (v.) Look up air at Dictionary.com
1520s, "expose to open air," 1520s, from air (n.1). Figurative sense of "expose ostentatiously, make public" is from 1610s of objects, 1862 of opinions, grievances, etc. Meaning "to broadcast" (originally on radio) is from 1933. Related: Aired; airing.
air (n.2) Look up air at Dictionary.com
1590s, "manner, appearance" (as in an air of mystery); 1650s, "assumed manner, affected appearance" (especially in phrase put on airs, 1781), from French air "look, appearance, mien, bearing, tone" (Old French aire "reality, essence, nature, descent, extraction" (12c.); compare debonair), which is perhaps from Latin ager "place, field, productive land" (see acre) on notion of "place of origin."

But some French sources connect this Old French word with the source of air (n.1), and it also is possible these senses in English developed from or were influenced by air (n.1); compare sense development of atmosphere and Latin spiritus "breath, breeze," also "high spirit, pride," and the extended senses of anima.
air (n.3) Look up air at Dictionary.com
"melody, tune, connected rhythmic succession of distinct musical sounds," 1580s, nativized from Italian aria (see aria), perhaps via French.
air force (n.) Look up air force at Dictionary.com
1917, from air (n.1) + force (n.); first attested with creation of the Royal Air Force. There was no United States Air Force until after World War II. The Air Corps was an arm of the U.S. Army. In 1942, the War Department reorganized it and renamed it Army Air Forces. The National Security Act of 1947 created the Department of the Air Force, headed by a Secretary of the Air Force, and the U.S.A.F.
air mail (n.) Look up air mail at Dictionary.com
also air-mail, airmail, 1913, from air (n.1) meaning "by aircraft" + mail (n.1). As a verb by 1942. Related: Air-mailed.
air-bag (n.) Look up air-bag at Dictionary.com
sealed bag filled with air, 1836, from air (n.1) + bag (n.). In early use a means of raising sunken ships, etc.; as an automobile safety feature by 1970.
air-brake (n.) Look up air-brake at Dictionary.com
brake that works by compressed air power, 1872, from air (n.1) + brake (n.1). Related: Air-brakes.
air-brush (n.) Look up air-brush at Dictionary.com
also airbrush, "atomizer used for spraying liquid ink or paint," 1883, from air (n.1) + brush (n.1). Invented a few years earlier but called at first paint distributer; renamed by U.S. manufacturer Liberty Walkup, who improved the design. As a verb by 1902. Related: Airbrushed; airbrushing.
air-conditioner (n.) Look up air-conditioner at Dictionary.com
from air (n.1) + conditioner. Along with air-conditioning, first attested 1909, originally an industrial process; its use in residences and office buildings is from the 1930s. An earlier name for such a device (using ice and fans) was air cooler (1875).
air-freshener (n.) Look up air-freshener at Dictionary.com
1949, from air (n.1) + agent noun from freshen.
air-gun (n.) Look up air-gun at Dictionary.com
1753, "gun in which condensed air propels the ball or bullet," 1753, from air (n.1) + gun (n.).
air-hole (n.) Look up air-hole at Dictionary.com
1766, from air (n.1) + hole (n.).
air-lock (n.) Look up air-lock at Dictionary.com
1857, from air (n.1) + lock (n.1) in the canal sense.
air-mattress (n.) Look up air-mattress at Dictionary.com
1949, from air (n.1) + mattress.
air-port (n.2) Look up air-port at Dictionary.com
"small opening in the side of a ship to admit air and light," 1788, from air (n.1) + port (n.2).
air-pump (n.) Look up air-pump at Dictionary.com
1650s, from air (n.1) + pump (n.1).
air-raid (n.) Look up air-raid at Dictionary.com
1914, from air (n.1) meaning "by aircraft" + raid (n.); originally in reference to British attacks Sept. 22, 1914, on Zeppelin bases at Cologne and Düsseldorf in World War I. The German word is Fliegerangriff "aviator-attack," and if Old English had survived into the 20th century our word instead might be fleogendeongrype.
One didn't dare to inhale for fear of breathing it in. It was the sound of eighteen hundred airplanes approaching Hamburg from the south at an unimaginable height. We had already experienced two hundred or even more air raids, among them some very heavy ones, but this was something completely new. And yet there was an immediate recognition: this was what everyone had been waiting for, what had hung for months like a shadow over everything we did, making us weary. It was the end. [Hans Erich Nossack, "Der Untergang," 1942]
air-rifle (n.) Look up air-rifle at Dictionary.com
rifle that uses compressed air power to fire the projectile, 1902, from air (n.1) + rifle (n.).
air-shaft (n.) Look up air-shaft at Dictionary.com
long narrow passage for admitting air, 1690s, from air (n.1) + shaft (n.2).
air-space (n.) Look up air-space at Dictionary.com
1889, from air (n.1) + space (n.).
airborne (adj.) Look up airborne at Dictionary.com
also air-borne, 1640s, "carried through the air," from air (n.1) + borne. Of military units, from 1937.
aircraft (n.) Look up aircraft at Dictionary.com
1850, originally in reference to airships and balloons, from air (n.1) + craft (n.). An image from boating, as were many early aviation words. Of airplanes from 1907 and since 1930s exclusively of them. Aircraft carrier is attested from 1919, in reference to H.M.S. Hermes, launched September 1919, the first ship built from the hull up as an aircraft carrier.
Airedale Look up Airedale at Dictionary.com
type of terrier, 1880, named for Airedale, a district in West Riding, Yorkshire. The place name is from the river Aire, which bears a name of uncertain origin.
Name registered by Kennel Club (1886), for earlier Bingley (where first bred), or broken-haired terrier. [Weekley]
airfoil (n.) Look up airfoil at Dictionary.com
1922, U.S. form of aerofoil.
airhead (n.) Look up airhead at Dictionary.com
"empty-headed person," 1972, from air (n.1) + head (n.). Earlier as a term in mining (mid-19c.) and as a military term (1950) based on beachhead.
airily (adv.) Look up airily at Dictionary.com
1766, "pretentiously jaunty," from airy "with ostentatious air" + -ly (2).