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    invalidity (n.) — I.Q.

    invalidity (n.)

    "want of energy, force, or efficiency," 1540s, from French invalidité (16c.) or directly from Medieval Latin invaliditas "weakness, infirmity," from Latin invalidus "not strong, weak, feeble" (see invalid (adj.1)).ETD invalidity (n.).2

    invalid (adj.2)

    "of no legal force," 1630s, from special use of Latin invalidus "not strong, infirm, impotent, feeble, inadequate," from in- "not" (see in- (1)) + validus "strong" (from PIE root *wal- "to be strong").ETD invalid (adj.2).2

    invalidate (v.)

    "destroy the strength or validity of, render of no force or effect," 1640s, from invalid (adj.2) + -ate (2). Related: Invalidated; invalidating.ETD invalidate (v.).2

    invalid (adj.1)

    "not strong, infirm," also "infirm from sickness, disease, or injury", 1640s, from Latin invalidus "not strong, infirm, impotent, feeble, inadequate," from in- "not" (see in- (1)) + validus "strong" (from PIE root *wal- "to be strong"). With pronunciation from French invalide (16c.).ETD invalid (adj.1).2

    invaluable (adj.)

    1570s, "above value, too valuable for exact estimate," from in- (1) "not" + value (v.) "estimate the worth of" + -able. It also has been used in a sense "without value, worthless" (1630s, from in- + valuable). Related: Invaluably.ETD invaluable (adj.).2

    invariant (adj.)

    "remaining always the same, not varying or changing," 1795, from in- (1) "not" + variant (adj.). As a noun, in mathematics, from 1851. Related: Invariance.ETD invariant (adj.).2

    invariable (adj.)

    "constant, uniform, unchanging," early 15c., from Old French invariable (14c.) and directly from Medieval Latin invariabilis, from in- "not, opposite of" (see in- (1)) + variabilis "changeable" (see variable). Related: Invariably.ETD invariable (adj.).2

    invariability (n.)

    "lack of variability or of liability to change," 1640s, from invariable + -ity. Invariableness is from 1650s.ETD invariability (n.).2

    invasive (adj.)

    "tending to invade, aggressive," mid-15c., invasif, from Old French invasif (15c.) or directly from Medieval Latin invasivus "invasive," from invas-, past-participle stem of invadere "go into; attack, invade," from in- "in" (from PIE root *en "in") + vadere "go, walk" (see vamoose).ETD invasive (adj.).2

    invective (n.)

    "an attacking in words," 1520s, from Medieval Latin invectiva "abusive speech," from Late Latin invectivus "abusive, scolding" from invect-, past-participle stem of invehere "to bring in, carry in, introduce," also "assault, assail," from in- "against" (see in- (1)) + vehere "to carry" (from PIE root *wegh- "to go, move, transport in a vehicle"). For nuances of usage, see humor (n.). The earlier noun form in English was inveccion (mid-15c.), and invective (adj.) was in Middle English.ETD invective (n.).2

    inveigh (v.)

    formerly also enveigh, late 15c., "to introduce," from Latin invehere "to bring in, carry in, introduce," also "assault, assail," from in- "against" (see in- (1)) + vehere "to carry" (from PIE root *wegh- "to go, move, transport in a vehicle"). Meaning "to give vent to violent denunciation" is from 1520s, from a secondary sense in Latin (see invective). Related: Inveighed; inveighing.ETD inveigh (v.).2

    inveigle (v.)

    formerly also enveigle, etc., late 15c., "to blind (someone's) judgment," apparently an alteration of French aveugler "delude, make blind," from Vulgar Latin *aboculus "without sight, blind," from Latin ab- "off, away from" (see ab-) + oculus "eye" (from PIE root *okw- "to see"). The Latin word is a loan-translation of Greek ap ommaton "without eyes." Meaning "to win over by deceit, seduce" is 1530s. Related: Inveigler; inveiglement.ETD inveigle (v.).2

    invent (v.)

    c. 1500, "to find, discover" (obsolete), a back-formation from invention or else from Latin inventus, past participle of invenire "to come upon; devise, discover."ETD invent (v.).2

    The general sense of "make up, fabricate, concoct, devise" (a plot, excuse, etc.) is from 1530s, as is that of "produce by original thought, find out by original study or contrivance." Related: Invented; inventing.ETD invent (v.).3

    inventive (adj.)

    early 15c., "skilled in invention," from Old French inventif (15c.), from Latin invent-, past-participle stem of invenire "devise, discover, find" (see invention). Related: Inventively; inventiveness.ETD inventive (adj.).2

    invention (n.)

    early 15c., invencioun, "finding or discovering of something," from Old French invencion (13c.) and directly from Latin inventionem (nominative inventio) "faculty of invention," noun of action from past-participle stem of invenire "to come upon, find; find out; invent, discover, devise; ascertain; acquire, get, earn," from in- "in, on" (from PIE root *en "in") + venire "to come" (from a suffixed form of PIE root *gwa- "to go, come").ETD invention (n.).2

    The sense of "thing invented" is first recorded 1510s; that of "act or process of finding out how to make or do" is from 1530s.ETD invention (n.).3

    The earliest sense of the word in Middle English was "devised method of organization" (c. 1400), a sense now obsolete. The meaning "finding or discovery of something" is preserved in Invention of the Cross, Church festival (May 3) celebrating the reputed finding of the Cross of the Crucifixion by Helena, mother of Constantine, in 326 C.E. The related classical Latin word for "a device, contrivance" was inventum.ETD invention (n.).4

    inventor (n.)

    c. 1500, "a discoverer, one who finds out" (now obsolete), from Latin inventor (fem. inventrix, source of French inventeur (15c.), Spanish inventor, Italian inventore) "contriver, author, discoverer, proposer, founder," agent noun from past-participle stem of invenire "to come upon, find; find out; invent, discover, devise; ascertain; acquire, get earn," from in- "in, on" (from PIE root *en "in") + venire "to come," from a suffixed form of PIE root *gwa- "to go, come." Meaning "one who contrives or produces a new thing or process" is from 1550s.ETD inventor (n.).2

    inventory (n.)

    early 15c., from Old French inventoire "detailed list of goods, a catalogue" (15c., Modern French inventaire), from Medieval Latin inventorium, alteration of Late Latin inventarium "list of what is found," from Latin inventus, past participle of invenire "to find, discover, ascertain" (see invention).ETD inventory (n.).2

    The form was altered in Medieval Latin by influence of words in -orium, which became very common in post-classical and Christian use. It properly belongs with words in -ary, and French has corrected the spelling. Related: Inventorial; inventorially.ETD inventory (n.).3

    inventory (v.)

    "make a list or catalogue of," c. 1600, from inventory (n.). Related: Inventoried; inventorying.ETD inventory (v.).2


    literally "mouth of the (River) Ness (probably from an Old Celtic word meaning "roaring one"), from Inver-, element in place names in Scotland of Gaelic origin, usually of places at the confluence of a river with another or the sea, from Old Irish *in(d)ber- "estuary," literally "a carrying in," from Celtic *endo-ber-o-, from *endo- "in" (from PIE *en-do-, extended form of root *en; see in) + from *ber- "to carry," from PIE root *bher- (1) "to carry," also "to bear children."ETD Inverness.2

    inveracity (n.)

    "lack of truthfulness; an untruth," 1789, from in- (1) "not, opposite of" + veracity.ETD inveracity (n.).2

    inverse (adj.)

    "turned in the opposite direction, having an opposite course or tendency," in early use also enverse, mid-15c., from Latin inversus, past participle of invertere "turn about, turn upside-down, upset, reverse, invert" (see invert). Related: Inversely. As a noun, "inverted state or condition," 1680s, from the adjective.ETD inverse (adj.).2

    inversion (n.)

    1550s, "act of inverting;" 1590s, "state of being inverted," from Latin inversionem (nominative inversio) "an inversion," noun of action from past participle stem of invertere "turn about, turn upside-down" (see invert). Meteorological sense is from 1902. In old psychology, "homosexuality" (1895, short for sexual inversion) but in later psychology "identification with the opposite sex" (1958).ETD inversion (n.).2

    invert (v.)

    "to turn (something) in an opposite direction; reverse the position, order, or sequence of," 1530s, from French invertir or directly from Latin invertere "turn upside down, turn about; upset, reverse, transpose," figuratively "pervert, corrupt, misrepresent," of words, "to use ironically," from in- "in, on" (from PIE root *en "in") + vertere "to turn" (from PIE root *wer- (2) "to turn, bend"). Related: Inverted; inverting; invertedly.ETD invert (v.).2

    invertebrate (adj.)

    "having naturally no backbone," 1819, from Latin in- "not" (see in- (1)) + vertebratus (Pliny), from vertebra "joint or articulation of the body, joint of the spine" (see vertebra). As a noun, "an invertebrate animal," 1826.ETD invertebrate (adj.).2

    invest (v.)

    late 14c., "to clothe in the official robes of an office," from Latin investire "to clothe in, cover, surround," from in "in, into" (from PIE root *en "in") + vestire "to dress, clothe," from PIE *wes- (2) "to clothe," extended form of root *eu- "to dress."ETD invest (v.).2

    The meaning "use money to produce profit" is attested from 1610s in connection with the East Indies trade, and it is probably a borrowing of a special use of Italian investire (13c., from the same Latin root) via the notion of giving one's capital a new form. The figurative sense of "to clothe (with attributes)" is from c. 1600. The military meaning "to besiege, surround with hostile intent" also is from c. 1600. Related: Invested; investing.ETD invest (v.).3

    investment (n.)

    1590s, "act of putting on vestments" (a sense now found in investiture); later "act of being invested with an office, right, endowment, etc." (1640s); and "surrounding and besieging" of a military target (1811); from invest + -ment.ETD investment (n.).2

    Commercial sense of "an investing of money or capital" is from 1610s, originally in reference to the East India Company; general use is from 1740 in the sense of "conversion of money to property in hopes of profit," and by 1837 in the sense "amount of money invested." For evolution of the commercial senses, see invest.ETD investment (n.).3

    investigator (n.)

    1550s, a native agent-noun formation from investigate, or else from Latin investigator "he that searches into," agent noun from past participle stem of investigare "to trace out, search after" (see investigation). Related: Investigatorial.ETD investigator (n.).2

    investigable (adj.)

    "that may be investigated," c. 1400, from Late Latin investigabilis "that may be searched into," from Latin investigare "trace out, search after," from in- "in, into" (from PIE root *en "in") + vestigare "to track, trace," from vestigium "footprint, track" (see vestige).ETD investigable (adj.).2

    investigation (n.)

    early 15c., from Old French investigacion (14c.), from Latin investigationem (nominative investigatio) "a searching into, a searching for," noun of action from past participle stem of investigare "to trace out, search after," figuratively "search into, investigate," from in- "in, into" (from PIE root *en "in") + vestigare "to track, trace," from vestigium "a footprint, a track" (see vestige).ETD investigation (n.).2

    investigate (v.)

    c. 1500, back-formation from investigation or else from Latin investigatus, past participle of investigare "to trace out, search after," figuratively "search into, investigate," from in- "in, into" (from PIE root *en "in") + vestigare "to track, trace," from vestigium "footprint, track" (see vestige). Related: Investigated; investigating.ETD investigate (v.).2

    investigative (adj.)

    "of or pertaining to investigation, curious and deliberative in research," 1803, from Latin investigat-, past-participle stem of investigare (see investigation) + -ive. Journalism sense is from 1951.ETD investigative (adj.).2

    investiture (n.)

    late 14c., "ceremony of clothing in the insignia of office," from Medieval Latin investitura "an investing," from past participle stem of Latin investire "to clothe" (see invest). Related: Investive.ETD investiture (n.).2

    investor (n.)

    1580s, "one who clothes;" 1862, "one who invests money," agent noun from invest.ETD investor (n.).2

    inveterate (adj.)

    late 14c., "old," from Latin inveteratus "of long standing, chronic, old," past participle of inveterare "become old in," from in- "in, into" (from PIE root *en "in") + verb from vetus (genitive veteris) "old" (see veteran). From early 15c. as "firmly established by long continuance;" from c. 1500, of persons, "hardened, confirmed" (in habit, etc.). Related: Inveterateness.ETD inveterate (adj.).2

    inveteracy (n.)

    "long continuance," 1690s, from inveterate + abstract noun suffix -cy.ETD inveteracy (n.).2

    inviable (adj.)

    1909, in biology, from in- (1) "not" + viable. Related: Inviability.ETD inviable (adj.).2


    Latin adjective, "unconquered, unsubdued, invincible," from in- "not, opposite of" (see in- (1)) + victus, past participle of vincere "to conquer, overcome" (from nasalized form of PIE root *weik- (3) "to fight, conquer").ETD invictus.2

    invidious (adj.)

    c. 1600, from Latin invidiosus "full of envy, envious" (also "exciting hatred, hateful"), from invidia "envy, grudge, jealousy, ill will" (see envy (n.)). Envious is the same word, but passed through French. Related: Invidiously; invidiousness.ETD invidious (adj.).2

    invigilate (v.)

    "to watch diligently" (archaic), 1550s, from Latin invigilatus, past participle of invigilare "watch over, be watchful, be devoted," from in- "in" (from PIE root *en "in") + vigilare "to watch, keep awake, not sleep" (from PIE root *weg- "to be strong, be lively"). In late 19c. especially in reference to student exams. Related: Invigilated; invigilating.ETD invigilate (v.).2

    invigilator (n.)

    1890, agent noun from invigilate.ETD invigilator (n.).2

    invigilation (n.)

    "the act of watching," 1871, noun of action from invigilate (v.). Perhaps from German, where it is used earlier than in English.ETD invigilation (n.).2

    invigorating (adj.)

    1690s, adjective from present participle of invigorate. Related: Invigoratingly.ETD invigorating (adj.).2

    invigorate (v.)

    1640s, from in- (2) + vigor (n.) + -ate (2). Earlier verb was envigor (1610s), from Old French envigorer. Related: Invigorated; invigorating.ETD invigorate (v.).2

    invigoration (n.)

    1660s, noun of action from invigorate. Perhaps modeled on French invigoration.ETD invigoration (n.).2

    invincibility (n.)

    1670s, from invincible + -ity. Invincibleness is recorded from 1610s.ETD invincibility (n.).2

    invincible (adj.)

    early 15c., from Old French invincible (14c.) or directly from Latin invincibilis "unconquerable," from in- "not" (see in- (1)) + vincibilis "to be gained, easily maintained, conquerable," from vincere "to overcome" (from nasalized form of PIE root *weik- (3) "to fight, conquer"). Related: Invincibly.ETD invincible (adj.).2

    The noun meaning "one who is invincible" is from 1630s. Invincible ignorance, an ignorance which the person having it lacks means to overcome, is from Church Latin ignorantia invincibilis (Aquinas). The Invincible Armada was the Spanish of 1588. Related: Invincibly.ETD invincible (adj.).3

    inviolate (adj.)

    "unbroken, intact," early 15c., from Latin inviolatus "unhurt," from in- "not, opposite of" (see in- (1)) + violatus (see violation).ETD inviolate (adj.).2

    inviolable (adj.)

    mid-15c., "that is to be kept without violation" (of an oath, etc.), from Latin inviolabilis "inviolable, invulnerable," from in- "not, opposite of" (see in- (1)) + violabilis "that may be injured, easily wounded," from violare "to do violence to" (see violation). Meaning "having a right or guaranty of immunity" (of a place of sanctuary, etc.) is from 1570s. Meaning "incapable of being injured" is from 1520s. Related: Inviolably.ETD inviolable (adj.).2

    inviolability (n.)

    1660s, from inviolable + -ity.ETD inviolability (n.).2

    invision (n.)

    "want of vision," 1640s, from in- (1) "not, opposite of" + vision (n.).ETD invision (n.).2

    invisible (adj.)

    mid-14c., "not perceptible to sight, incapable of being seen," from Old French invisible (13c.), from Latin invisibilis "unseen, not visible," from in- "not" (see in- (1)) + visibilis (see visible). Meaning "kept out of sight" is from 1640s. As a noun, "things invisible," from 1640s. Invisible Man is from H.G. Wells's novel (1897); invisible ink is from 1680s. Related: Invisibly.ETD invisible (adj.).2

    invisibility (n.)

    1560s, from Late Latin invisibilitas, from Latin invisibilis "not visible, unseen" (see invisible).ETD invisibility (n.).2

    invitation (n.)

    mid-15c., "act of inviting, solicitation," from Latin invitationem (nominative invitatio) "an invitation, incitement, challenge," noun of action from past participle stem of invitare "invite, treat, entertain," originally "be pleasant toward," from in- "toward" (from PIE root *en "in").ETD invitation (n.).2

    The second element is obscure. Watkins suggests a suffixed form of the PIE root *weie- "to go after something, pursue with vigor" (see gain (v.)); de Vaan also traces it to a PIE form meaning "pursued." Meaning "the spoken or written form in which a person is invited" is from 1610s.ETD invitation (n.).3

    invite (v.)

    "solicit to come," 1530s, a back-formation from invitation, or else from French inviter (15c.), from Latin invitare "to invite," also "to summon, challenge; to feast, to entertain," a word of uncertain origin. Related: Invited; inviting.ETD invite (v.).2

    invite (n.)

    "an invitation," 1650s, from invite (v.).ETD invite (n.).2

    inviting (adj.)

    "attractive, alluring," c. 1600, present-participle adjective from invite (v.). Related: Invitingly.ETD inviting (adj.).2

    invitational (adj.)

    1894, from invitation + -al (1). The noun is by 1940, short for invitational tournament.ETD invitational (adj.).2

    invita Minerva

    Latin adverbial phrase, used with reference to literary or artistic creation, "without inspiration," literally "Minerva unwilling;" i.e. "without inspiration from the goddess of wisdom;" ablative fem. of invitus "against the will, unwilling, reluctant," according to de Vaan from PIE compound *n-uih-to- "not turned to, not pursuing," related to the source of invitation. With Minervā, ablative absolute of Minerva.ETD invita Minerva.2

    invitatory (adj.)

    "using or containing invitation," 1640s, from Latin invitatorius "inviting," from invitat-, past-participle stem of invitare "to invite, treat, entertain" (see invitation).ETD invitatory (adj.).2

    invitee (n.)

    1837, from invite (v.) + -ee.ETD invitee (n.).2

    in vitro

    1892, scientific Latin; "in a test tube, culture dish, etc.;" literally "in glass," from Latin vitrum "glass" (see vitreous).ETD in vitro.2

    in vivo

    1898, Latin; "within a living organism," from vivere "to live" (see vital).ETD in vivo.2

    invocation (n.)

    late 14c., "petition (to God or a god) for aid or comfort; invocation, prayer;" also "a summoning of evil spirits," from Old French invocacion "appeal, invocation" (12c.), from Latin invocationem (nominative invocatio), noun of action from past participle stem of invocare "to call upon, invoke, appeal to" (see invoke).ETD invocation (n.).2

    invoice (n.)

    "written account of the particulars and prices of merchandise shipped or sent," 1550s, apparently from a re-Latinized form of French envois, plural of envoi "dispatch (of goods)," literally "a sending," from envoyer "to send," from Vulgar Latin *inviare "send on one's way," from Latin in "on" (from PIE root *en "in") + via "road" (see via (adv.)). As a verb, 1690s, from the noun.ETD invoice (n.).2

    invoke (v.)

    late 15c., from Old French invoquer, envoquer, envochier "invoke, implore" (12c.), from Latin invocare "call upon, implore," from in- "upon" (from PIE root *en "in") + vocare "to call," which is related to vox (genitive vocis) "voice" (from PIE root *wekw- "to speak"). Related: Invoked; invoking.ETD invoke (v.).2

    involuntary (adj.)

    mid-15c., from Late Latin involuntarius "involuntary, unwilling," from in- "not, opposite of" (see in- (1)) + Latin voluntarius "willing, voluntarily" (see voluntary). Related: Involuntarily.ETD involuntary (adj.).2

    involution (n.)

    late 14c., "condition of being twisted or coiled; a fold or entanglement," originally in anatomy, from Late Latin involutionem (nominative involutio) "a rolling up," noun of action from past participle stem of Latin involvere "envelop, surround, roll into" (see involve). Related: Involutional.ETD involution (n.).2

    involute (adj.)

    early 15c., "wrapped," from Latin involutus "rolled up, intricate, obscure," past participle of involvere "envelop, surround; roll into, wrap up" (see involve).ETD involute (adj.).2

    involve (v.)

    late 14c., "envelop, surround; make cloudy or obscure," from Old French involver and directly from Latin involvere "envelop, surround, overwhelm," literally "roll into," from in- "in" (from PIE root *en "in") + volvere "to roll," from PIE root *wel- (3) "to turn, revolve." Mid-15c. as "concern oneself." Sense of "take in, include" first recorded c. 1600. Related: Involved; Involving.ETD involve (v.).2

    involvement (n.)

    1706, from involve + -ment.ETD involvement (n.).2

    involved (adj.)

    "complicated," 1640s, past-participle adjective from involve. Earlier it meant "spirally curved" (1610s).ETD involved (adj.).2

    invulnerability (n.)

    1707, from invulnerable + -ity.ETD invulnerability (n.).2

    invulnerable (adj.)

    1590s, from Latin invulnerabilis "invulnerable," from in- "not" (see in- (1)) + vulnerabilis (see vulnerable). Related: Invulnerably.ETD invulnerable (adj.).2

    inward (adj.)

    Old English inweard "inmost; sincere; internal, intrinsic; deep," from Proto-Germanic *inwarth "inward" (source also of Old Norse innanverðr, Old High German inwart, Middle Dutch inwaert), from root of Old English inne "in" (see in (adv.)) + -weard (see -ward). As an adverb, Old English inneweard. As a noun in late Old English, "entrails, intestines."ETD inward (adj.).2

    inwardness (n.)

    late 14c., from inward + -ness.ETD inwardness (n.).2

    inwardly (adv.)

    Old English inweardlice; see inward + -ly (2).ETD inwardly (adv.).2

    inwit (n.)

    "inward awareness of right or wrong" (a word formed to translate Latin conscientia), early 13c., "conscience;" c. 1300, "reason, intellect," from in (adj.) + wit (n.).ETD inwit (n.).2

    Not related to Old English inwit, which meant "deceit." Joyce's use of it in "Ulysses" (1922) echoes the title of the 14c. work "Ayenbite of Inwyt" ("Remorse of Conscience," a translation from French) and is perhaps the best-known example of the modern use of the word as a conscious archaism, but it is not the earliest.ETD inwit (n.).3

    inwork (v.)

    1680s, from in (adv.) + work (v.).ETD inwork (v.).2


    in Greek mythology, daughter of the river god Inachus, she was pursued by Zeus, who changed her to a heifer in a bid to escape the notice of Juno, but she was tormented by a gadfly sent by Juno.ETD Io.2

    The Jovian moon was discovered in 1610; the mythological names for all of them (objects of Jupiter's seductions in the myths) were proposed shortly thereafter but not widely used before mid-19c. (Compare Titan).ETD Io.3

    iodic (adj.)

    1815, from French iodic (1812); see iodine + -ic.ETD iodic (adj.).2

    iodide (n.)

    compound of iodine, 1822, from iod-, combining form of iodine used before vowels + -ide.ETD iodide (n.).2

    iodine (n.)

    non-metallic element, 1814, formed by English chemist Sir Humphry Davy from French iode "iodine," which was coined 1812 by French chemist Joseph Louis Gay-Lussac from Greek iōeidēs "violet-colored" (from ion "the violet; dark blue flower;" see violet) + eidos "appearance" (see -oid).ETD iodine (n.).2

    Davy added the chemical suffix -ine (2) to make it analogous with chlorine and fluorine. So called from the color of the vapor given off when the crystals are heated.ETD iodine (n.).3

    iodize (v.)

    "add iodine to, treat with iodine," 1841, from iodine + -ize. Related: Iodized; iodizing.ETD iodize (v.).2


    word-forming element attached to verbs, making nouns of state, condition, or action, from French -ion or directly from Latin -ionem (nominative -io, genitive -ionis), common suffix forming abstract nouns from verbs.ETD -ion.2

    ion (n.)

    1834, introduced by English physicist and chemist Michael Faraday (suggested by the Rev. William Whewell, English polymath), coined from Greek ion, neuter present participle of ienai "go," from PIE root *ei- "to go." So called because ions move toward the electrode of opposite charge.ETD ion (n.).2

    Ionian (adj.)

    1590s, "of Ionia," the districts of ancient Greece inhabited by the Ionians, one of the three (or four) great divisions of the ancient Greek people. The name (which Herodotus credits to an ancestral Ion, son of Apollo and Creusa) probably is pre-Greek, perhaps related to Sanskrit yoni "womb, vulva," and a reference to goddess-worshipping people. As a noun from 1560s.ETD Ionian (adj.).2

    Ionia included Attica, Euboea, and the north coast of the Peloponnesus, but it especially referred to the coastal strip of Asia Minor, including the islands of Samos and Chios. The old Ionic dialect was the language of Homer and Herodotus, and, via its later form, Attic, that of all the great works of the Greeks. The name also was given to the sea that lies between Sicily and Greece, and the islands in it (1630s in English in this sense). The musical Ionian mode (1844) corresponds to our C-major scale but was characterized by the Greeks as soft and effeminate, as were the Ionians generally.ETD Ionian (adj.).3

    Ionic (adj.)

    "pertaining to Ionia or the Ionians," 1570s of music; 1580s of architecture, from Latin Ionicus, from Greek Ionikos (see Ionian). In prosody, a foot of two long syllables followed by two short. The Ionic school of philosophers (Thales, Anaxamander, etc.) studied the material world in ways that somewhat anticipated observational science. It also once was the name of an important school of Greek painting, but all of it save the name is lost. Related: Ionicize (1841).ETD Ionic (adj.).2

    ionization (n.)

    1891; see ionize + noun ending -ation.ETD ionization (n.).2

    ionize (v.)

    1896, from ion + -ize. Related: Ionized; ionizing. Unrelated to Ionize "to make Ionic in form or fact" (1816), for which see Ionian.ETD ionize (v.).2

    ionosphere (n.)

    region of the outer atmosphere, 1926, from ion + sphere. Coined by Scottish radar pioneer Robert A. Watson-Watt (1892-1973). So called because it contains many ions.ETD ionosphere (n.).2

    iopterous (adj.)

    "having violet wings," 1855, from Greek ion "violet, violet color" (see iodine) + pteron "wing" (from PIE root *pet- "to rush, to fly").ETD iopterous (adj.).2

    iota (n.)

    "very small amount," 1630s, figurative use of iota, ninth and smallest letter in the Greek alphabet (corresponding to Latin -i-). Its use in this sense is after Matthew v.18 (see jot (n.), which is the earlier form of the name in English), but iota in classical Greek also was proverbially used of anything very small. The letter name is from Semitic (compare Phoenician and Hebrew yodh).ETD iota (n.).2


    also I.O.U., I O U, 1610s, originally written IOV (see V); a punning on "I Owe You." "A memorandum or acknowledgement of debt less formal than a promissory note, because no direct promise to pay is expressed." [Century Dictionary]ETD IOU.2


    organized as a U.S. territory 1838; admitted as a state 1846, named for the river, ultimately from the name of the native people, of the Chiwere branch of the Siouan family; said to be from Dakota ayuxba "sleepy ones," or from an Algonquian language (Bright cites Miami/Illinois /aayohoowia/). On a French map of 1673 it appears as Ouaouiatonon. John Quincy Adams, in his diary entries on the House of Representatives debate on the territorial bill in 1838, writes it Ioway. Related: Iowan.ETD Iowa.2

    IPA (n.)

    also I.P.A., 1952, abbreviation of India pale ale.ETD IPA (n.).2

    ipecac (n.)

    dried root of a South American shrub, used as an emetic, purgative, nauseant, etc., 1710, borrowing via Portuguese of a shortened form of Tupi ipecacuana (a word attested in English from 1682), a medicinal plant of Brazil. The Indian word is said to mean "small plant causing vomit."ETD ipecac (n.).2

    ipse dixit

    Latin, literally "he (the master) said it," translation of Greek autos epha, phrase used by disciples of Pythagoras when quoting their master. Hence, "an assertion made without proof, resting entirely on the authority of the speaker" (1590s), ipsedixitism "practice of dogmatic assertion" (1830, Bentham), etc.ETD ipse dixit.2

    ipseity (n.)

    "personal identity, individuality, selfhood," 1650s, from Latin ipse "self" + -ity.ETD ipseity (n.).2

    ipsilateral (adj.)

    "on the same side of the body," 1907, from Latin ipse "self" + lateral (adj.). Related: Ipsilaterally.ETD ipsilateral (adj.).2

    ipso facto

    Latin adverbial phrase, literally "by that very fact, by the fact itself," from neuter ablative of ipse "he, himself, self" + ablative of factum "fact" (see fact).ETD ipso facto.2


    1922, abbreviation of intelligence quotient, a 1921 translation of German Intelligenz-quotient, coined 1912 by German psychologist William L. Stern.ETD I.Q..2

    Earlier, i.q. was an abbreviation of Latin idem quod "the same as."ETD I.Q..3

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