epistaxis (n.) Look up epistaxis at Dictionary.com
medical Latin, from Greek epistaxis "nosebleeding," from epi "upon" (see epi-) + stazein- "to let fall in drops" (see stalactite).
epistemic (adj.) Look up epistemic at Dictionary.com
1922, from Greek episteme "knowledge" (see epistemology) + -ic.
epistemology (n.) Look up epistemology at Dictionary.com
"theory of knowledge," 1856, coined by Scottish philosopher James F. Ferrier (1808-1864) from Greek episteme "knowledge," from Ionic Greek epistasthai "know how to do, understand," literally "overstand," from epi "over, near" (see epi-) + histasthai "to stand," (see histo-).

The scientific (as opposed to philosophical) study of the roots and paths of knowledge is epistemics (1969). Related: Epistemological; epistemologically.
epistle (n.) Look up epistle at Dictionary.com
Old English epistol, from Old French epistle, epistre (Modern French épitre), from Latin epistola "letter," from Greek epistole "message, letter, command, commission," whether verbal or in writing, from epistellein "send to," from epi "to" (see epi-) + stellein in its secondary sense of "to dispatch, send" from PIE *stel-yo-, suffixed form of root *stel- "to put, stand," with derivatives referring to a standing object or place (see stall (n.1)).

Also acquired in Old English directly from Latin as pistol. Specific sense of "letter from an apostle forming part of canonical scripture" is c.1200.
epistolary (adj.) Look up epistolary at Dictionary.com
1650s, from French épistolaire, from Latin epistolaris, from epistola (see epistle).
epistrophe (n.) Look up epistrophe at Dictionary.com
1640s, from Late Latin epistrophe, from Greek epistrophe "a turning about," from epi "upon" (see epi-) + strophe "a turning" (see strophe).
epitaph (n.) Look up epitaph at Dictionary.com
mid-14c., from Old French epitaphe (12c.) and directly from Medieval Latin epitaphium "funeral oration, eulogy," from Greek epitaphion "a funeral oration," noun use of neuter of epitaphos "of a funeral," from epi "at, over" (see epi-) + taphos "tomb, funeral rites," from PIE root *dhembh- "to bury." Among the Old English equivalents was byrgelsleoð.
epithalamium (n.) Look up epithalamium at Dictionary.com
1590s, "bridal song," from Latin epithalamium, from Greek epithalamion "a bridal song," from epi "at, upon" (see epi-) + thalamos "bridal chamber, inner chamber" (see thalamus).
epithelium (n.) Look up epithelium at Dictionary.com
1748, Modern Latin (Frederick Ruysch), from Greek epi "upon" (see epi-) + thele "teat, nipple" (see fecund). Related: Epithelial.
epithet (n.) Look up epithet at Dictionary.com
1570s, "descriptive name for a person or thing," from Middle French épithète or directly from Latin epitheton, from Greek epitheton "something added," adjective often used as noun, from neuter of epithetos "attributed, added," from epitithenai "to add on," from epi "in addition" (see epi-) + tithenai "to put" (see theme).
epitome (n.) Look up epitome at Dictionary.com
1520s, "an abstract; brief statement of the chief points of some writing," from Middle French épitomé (16c.), from Latin epitome "abridgment," from Greek epitome "abridgment," from epitemnein "cut short, abridge," from epi "into" (see epi-) + temnein "to cut" (see tome). Sense of "person or thing that typifies something" is first recorded c.1600.
epitomise (v.) Look up epitomise at Dictionary.com
chiefly British English spelling of epitomize. For spelling, see -ize. Related: Epitomising; epitomises.
epitomize (v.) Look up epitomize at Dictionary.com
1590s, "shorten, condense," from epitome + -ize. Meaning "typify, embody" is from 1620s. Related: Epitomized; epitomizing; epitomizes.
epizootic (n.) Look up epizootic at Dictionary.com
animal equivalent of epidemic, 1748, from French épizootique, from épizootie, irregularly formed from Greek epi (see epi-) + zoon (see zoo-).
epoch (n.) Look up epoch at Dictionary.com
1610s, epocha, "point marking the start of a new period in time" (such as the founding of Rome, the birth of Christ, the Hegira), from Late Latin epocha, from Greek epokhe "stoppage, fixed point of time," from epekhein "to pause, take up a position," from epi "on" (see epi-) + ekhein "to hold" (see scheme (n.)). Transferred sense of "a period of time" is 1620s; geological usage (not a precise measurement) is from 1802.
epochal (adj.) Look up epochal at Dictionary.com
1680s, from epoch + -al (1).
epode (n.) Look up epode at Dictionary.com
1590s, a kind of lyric poem in which a short line follows a longer one (invented by Archilochus, also used by Horace), from Latin epodos, from Greek epodus "after-song, incantation," from epi "after" (see epi-) + odein "to sing" (see ode).
eponym (n.) Look up eponym at Dictionary.com
one whose name becomes that of a place, a people, an era, an institution, etc., 1846, from Greek eponymos "given as a name, giving one's name to something," from epi "upon" (see epi-) + onyma, Aeolic dialectal variant of onoma "name" (see name (n.)).
eponymous (adj.) Look up eponymous at Dictionary.com
1846; see eponym + -ous.
epoxy (n.) Look up epoxy at Dictionary.com
1916, in reference to certain chemical compounds, from epi- + first element of oxygen (epoxy- is used as a prefix in chemistry). Resins from them are used as powerful glues. Hence the verb meaning "to bond with epoxy" (1965). Related: Epoxied.
epsilon (n.) Look up epsilon at Dictionary.com
from Greek, literally e psilon "bare -e-, -e- and nothing else," in contradistinction to the diphthong -ai-, which has the same sound. Greek psilon "smooth, simple" is of uncertain origin.
Epsom salts Look up Epsom salts at Dictionary.com
magnesium sulphate, 1770, obtained from Epsom water, the water of a mineral spring at Epsom in Surrey, England, the medicinal properties of which were discovered in Elizabethan times. The place name is recorded c.973 as Ebbesham, literally "Ebbi's homestead," from the name of some forgotten Anglo-Saxon. The mineral supply there was exhausted 19c.
Epstein-Barr virus Look up Epstein-Barr virus at Dictionary.com
1968, named for British virologist Michael Anthony Epstein and Irish-born virologist Yvonne M. Barr.
ept (adj.) Look up ept at Dictionary.com
1938, back-formation from inept, usually with an attempt at comical effect. Related: Eptitude; eptly.
equability (n.) Look up equability at Dictionary.com
1530s, from Latin aequabilitas, from aequabilis (see equable).
equable (adj.) Look up equable at Dictionary.com
1670s, back-formation from equability or else from Latin aequabilis "equal, consistent, uniform," from aequare "make uniform" (see equate).
equal (adj.) Look up equal at Dictionary.com
late 14c., from Latin aequalis "uniform, identical, equal," from aequus "level, even, just," of unknown origin. Parallel formation egal (from Old French egal) was in use late 14c.-17c. The noun is recorded from 1570s.
equal (v.) Look up equal at Dictionary.com
1580s, "compare, liken," also "match, rival," from equal (adj.). Related: Equaled; equaling.
equalitarian (adj.) Look up equalitarian at Dictionary.com
1799, in reference to the doctrine that all mankind are equal, from equality on model of humanitarian, etc.
equality (n.) Look up equality at Dictionary.com
late 14c., "evenness of surface, uniformity of size;" c.1400, in reference to amount or number, from Old French equalité (Modern French égalité, which form dates from 17c.), from Latin aequalitatem (nominative aequalitas) "equality, similarity, likeness" (also sometimes with reference to civil rights), from aequalis (see equal (adj.)). Of privileges, rights, etc., from 1520s.
equalization (n.) Look up equalization at Dictionary.com
1793, from equalize + -ation.
equalize (v.) Look up equalize at Dictionary.com
1580s, from equal (adj.) + -ize. Related: Equalized; equalizing.
equalizer (n.) Look up equalizer at Dictionary.com
1792, agent noun from equalize. Sports sense attested by 1930; in the U.S. underworld slang sense of "pistol," it is from c.1900.
equally (adv.) Look up equally at Dictionary.com
late 14c., from equal (adj.) + -ly (2).
equanimity (n.) Look up equanimity at Dictionary.com
c.1600, "fairness, impartiality," from French équanimité, from Latin aequanimitatem (nominative aequanimitas) "evenness of mind, calmness," from aequus "even, level" (see equal (adj.)) + animus "mind, spirit" (see animus). Meaning "evenness of temper" in English is from 1610s.
equanimous (adj.) Look up equanimous at Dictionary.com
1650s, from Latin aequanimis (see equanimity) + -ous.
equate (v.) Look up equate at Dictionary.com
early 15c., from Latin aequatus "level, levelled, even," past participle of aequare "make even or uniform, make equal," from aequus "level, even, equal" (see equal (adj.)). Earliest use in English was of astrological calculation, then "to make equal;" meaning "to regard as equal" is early 19c. Related: Equated; equating.
equation (n.) Look up equation at Dictionary.com
late 14c., a term in astrology; meaning "action of making equal" is from 1650s; mathematical sense is from 1560s, on notion of equalizing the expressions; from Latin aequationem (nominative aequatio) "an equal distribution, community," from past participle stem of aequare (see equal (adj.)). Chemistry sense is from 1807.
equator (n.) Look up equator at Dictionary.com
late 14c., from Medieval Latin aequator diei et noctis "equalizer of day and night" (when the sun is on the celestial equator, twice annually, day and night are of equal length), agent noun from Latin aequare "make equal" (see equate). Sense of "celestial equator" is earliest, extension to "terrestrial line midway between the poles" first recorded in English 1610s.
equatorial (adj.) Look up equatorial at Dictionary.com
1660s, from equator + -al (1).
equerry (n.) Look up equerry at Dictionary.com
1590s, short for groom of the equirrie, from esquiry "stables" (1550s), from Middle French escuerie (Modern French écurie), perhaps from Medieval Latin scuria "stable," from Old High German scura "barn;" or from Old French escuier "groom," from Vulgar Latin scutarius "shield-bearer." In either case, spelling influenced by Latin equus "horse," which is unrelated.
equestrian (adj.) Look up equestrian at Dictionary.com
1650s, formed in English from Latin equester (genitive equestris) "of a horseman," from eques "horseman, knight," from equus "horse" (see equine). As a noun, "one who rides on horseback," from 1791. The pseudo-French fem. equestrienne is attested from 1848.
equi- Look up equi- at Dictionary.com
word-forming element meaning "equal," from Latin aequi-, comb. form of aequus "equal, even" (see equal (adj.)).
equiangular (adj.) Look up equiangular at Dictionary.com
1650s; see equi- + angular.
equidistant (adj.) Look up equidistant at Dictionary.com
1560s, from French équidistant (14c.), from Late Latin aequidistantem (nominative aequidistans), from aequi- (see equal) + distantem (see distant). In reference to a type of map projection, from 1866.
equilateral (adj.) Look up equilateral at Dictionary.com
1560s, from Late Latin aequilateralis, from aequi- (see equal (adj.)) + lateralis (see lateral).
equilibrium (n.) Look up equilibrium at Dictionary.com
c.1600, from Latin aequilibrium, from aequus "equal" (see equal (adj.)) + libra "a balance, scale, plummet" (see Libra).
equine (adj.) Look up equine at Dictionary.com
1765, from Latin equinus, from equus "horse," from PIE root *ekwo- "horse" (cognates: Greek hippos, Old Irish ech, Old English eoh, Gothic aihwa-, Sanskrit açva-, Avestan aspa-, Old Church Slavonic ehu-, all meaning "horse").
equinox (n.) Look up equinox at Dictionary.com
late 14c., from Old French equinoce (12c.) or directly from Medieval Latin equinoxium "equality of night (and day)," from Latin aequinoctium "the equinoxes," from aequus "equal" (see equal (adj.)) + nox (genitive noctis) "night" (see night). The Old English translation was efnniht. Related: Equinoctial.
equip (v.) Look up equip at Dictionary.com
1520s, from Middle French équiper "to fit out," from Old French esquiper "fit out a ship" (12c.), probably from Old Norse skipa "fit out a ship," from skip "ship" (see ship (n.)). Related: Equipped; equipping. Spanish and Portuguese esquipar are from French.