semester (n.) Look up semester at Dictionary.com
1827, from German Semester "half-year course in a university," from Latin semestris, in cursus semestris "course of six months," from semestris, semenstris "of six months, lasting six months, half-yearly, semi-annual," from sex "six" (see six) + mensis "month" (see moon (n.)). Related: Semestral; semestrial.
semi- Look up semi- at Dictionary.com
before vowels sem-, word-forming element meaning "half, part, partly; partial, imperfect; twice," from Latin semi- "half," from PIE *semi- "half" (cognates: Sanskrit sami "half," Greek hemi- "half," Old English sam-, Gothic sami- "half").

Old English cognate sam- was used in such compounds as samhal "poor health," literally "half-whole;" samsoden "half-cooked," figuratively "stupid" (compare half-baked); samcucu "half-dead," literally "half-alive;" and the last survivor of the group, sandblind "dim-sighted" (q.v.). Common in Latin (as in semi-gravis "half-drunk," semi-hora "half hour," semi-mortuus "half-dead," semi-nudus "half-naked," semi-vir "half-man, hermaphrodite"). The Latin-derived form in English has been active in forming native words since 15c.
semi-annual (adj.) Look up semi-annual at Dictionary.com
also semiannual, 1775, from semi- + annual. Related: Semiannually.
semi-arid (adj.) Look up semi-arid at Dictionary.com
also semiarid, 1886, from semi- + arid.
semi-automatic (adj.) Look up semi-automatic at Dictionary.com
1853, from semi- + automatic (adj.). In reference to firearms, 1889.
semi-demi- Look up semi-demi- at Dictionary.com
word-forming element meaning "sixty-fourth part," 1660s; see semi- + demi-.
semi-detached (adj.) Look up semi-detached at Dictionary.com
in reference to houses, 1845, from semi- + past participle of detach (v.).
The "Detached House" bears its peculiar characteristic on its front; it stands alone, and nothing more can be said about it; but with the "semi-detached house" there is a subtle mystery, much to be marvelled at. Semi-detached! Have the party-walls between two houses shrunk, or is there a bridge connecting the two, as in Mr. Beckford's house in Landsdown Crescent, Bath? A semi-detached house may be a house with a field on one side and a bone-boiling factory on the other. Semi-detached may mean half-tumbling to pieces. I must inquire into it. ["Houses to Let," in "Household Words," March 20, 1852]
semi-monthly (adj.) Look up semi-monthly at Dictionary.com
also semimonthly, 1809, from semi- + monthly.
semi-official (adj.) Look up semi-official at Dictionary.com
1798, from semi- + official (adj.). Related: Semi-officially.
semi-permeable (adj.) Look up semi-permeable at Dictionary.com
1873, from semi- + permeable. Translating German halbdurchlässig.
semi-professional (adj.) Look up semi-professional at Dictionary.com
1824, from semi- + professional (adj.). As a noun from 1843. Related: Semi-professionally.
semi-solid (adj.) Look up semi-solid at Dictionary.com
1803, from semi- + solid (adj.).
semi-trailer (n.) Look up semi-trailer at Dictionary.com
also semitrailer, 1910 in reference to motor vehicles (late 19c. in botany), from semi- + trailer.Short form semi is attested from 1942.
semi-weekly (adj.) Look up semi-weekly at Dictionary.com
also semiweekly, "occurring twice a week," 1791, from semi- + weekly.
semicircle (n.) Look up semicircle at Dictionary.com
1520s, from semi- + circle (n.) or else from Latin semicirculus.
semicircular (adj.) Look up semicircular at Dictionary.com
early 15c., from Latin semicirculus (see semicircle) + -ar.
semicolon (n.) Look up semicolon at Dictionary.com
punctuation-mark, 1640s, a hybrid coined from Latin-derived semi- + Greek-based colon (n.1). The mark itself was in Greek the point of interrogation.
semiconductor (n.) Look up semiconductor at Dictionary.com
1838, "material whose electrical conductivity is between that of a conductor and that of an insulator," from semi- + conductor. Modern very specific sense is recorded from 1931.
semiconscious (adj.) Look up semiconscious at Dictionary.com
also semi-conscious, 1838, from semi- + conscious. Related: Semiconsciously; semiconsciousness.
semifinal (adj.) Look up semifinal at Dictionary.com
also semi-final, 1867, from semi- + final. As a noun from 1868.
seminal (adj.) Look up seminal at Dictionary.com
late 14c., "of seed or semen," from Old French seminal (14c.) and directly from Latin seminalis, from semen (genitive seminis) "seed" (see semen). Figurative sense of "full of possibilities" is attested from 1630s. Related: Seminally; seminality.
seminar (n.) Look up seminar at Dictionary.com
1887, "special group-study class for advanced students," from German Seminar "group of students working with a professor," from Latin seminarium "breeding ground, plant nursery" (see seminary). Sense of "meeting for discussion of a subject" first recorded 1944.
seminarian (n.) Look up seminarian at Dictionary.com
"seminary student," 1580s, from seminary + -ian.
seminary (n.) Look up seminary at Dictionary.com
mid-15c., "plot where plants are raised from seeds," from Latin seminarium "plant nursery, seed plot," figuratively, "breeding ground," from seminarius "of seed," from semen (genitive seminis) "seed" (see semen). Meaning "school for training priests" first recorded 1580s; commonly used for any school (especially academies for young ladies) from 1580s to 1930s.
semination (n.) Look up semination at Dictionary.com
1530s, "action of sowing, from Latin seminationem (nominative seminato) "a sowing, propagation," noun of action from past participle stem of seminare "to plant, propagate," from semen (genitive seminis) "seed" (see semen).
Seminole (n.) Look up Seminole at Dictionary.com
1763, from Creek (Muskogean) simano:li, earlier simalo:ni "wild, untamed, runaway," from American Spanish cimarron (see maroon (v.)). They fought ward against U.S. troops 1817-18 and 1835-42, after which they largely were removed to Indian Territory (Oklahoma).
semiology (n.) Look up semiology at Dictionary.com
1690s, "sign language," from Greek semeion "a sign, mark, token," from sema (compare semiotic) + -ology. As "branch of medical science concerned with symptoms," 1839; as "logical theory of signs" from 1923. Related: Semiological.
semiotic (adj.) Look up semiotic at Dictionary.com
1620s, "of symptoms, relating to signs of diseases," from Greek semeiotikos "significant," also "observant of signs," adjective form of semeiosis "indication," from semeioun "to signal, to interpret a sign," from semeion "a sign, mark, token," from sema "sign" (see semantic). Its use in psychology dates to 1923. Related: Semiotical (1580s).
semiotics (n.) Look up semiotics at Dictionary.com
study of signs and symbols with special regard to function and origin, 1880, from semiotic; also see -ics. Medical sense is from 1660s.
semiprecious (adj.) Look up semiprecious at Dictionary.com
also semi-precious, 1818, from semi- + precious (adj.).
semiquaver (n.) Look up semiquaver at Dictionary.com
"sixteenth-note," 1570s, from semi- + quaver (n.).
semisweet (adj.) Look up semisweet at Dictionary.com
also semi-sweet, 1943, from semi- + sweet.
Semite (n.) Look up Semite at Dictionary.com
1847, "a Jew, Arab, Assyrian, or Aramaean" (an apparently isolated use from 1797 refers to the Semitic language group), back-formation from Semitic or else from French Sémite (1845), from Modern Latin Semita, from Late Latin Sem "Shem," one of the three sons of Noah (Gen. x:21-30), regarded as the ancestor of the Semites (in old Bible-based anthropology), from Hebrew Shem. In modern sense said to have been first used by German historian August Schlözer in 1781.
Semitic (adj.) Look up Semitic at Dictionary.com
1797, denoting the language group that includes Hebrew, Arabic, Aramaic, Assyrian, etc.; 1826 as "of or pertaining to Semites," from Medieval Latin Semiticus (source of Spanish semitico, French semitique, German semitisch), from Semita (see Semite). As a noun, as the name of a linguistic family, from 1813. In non-linguistic use, perhaps directly from German semitisch. In recent use often with the specific sense "Jewish," but not historically so limited.
Semitism (n.) Look up Semitism at Dictionary.com
1848, "characteristic attributes of Semitic languages;" 1851, "characteristic attributes of Semitic people," from Semite + -ism. From 1870 as "Jewish influence in a society."
semitone (n.) Look up semitone at Dictionary.com
c.1600, from semi- + tone (n.) in the musical sense.
semolina (n.) Look up semolina at Dictionary.com
meal from hard kernels of wheat, 1797, alteration of Italian semolino "grits; paste for soups," diminutive of semola "bran," from Latin simila "the finest flour," probably from the same Semitic source as Greek semidalis "the finest flour" (compare Assyrian samidu, Syrian semida "fine meal").
semper idem Look up semper idem at Dictionary.com
Latin, literally "always the same;" see semper- + identical.
semper- Look up semper- at Dictionary.com
word-forming element meaning "always, ever," from Latin semper "always, ever, at all times, continuously" (literally "once for all"), from PIE *sem- (1) "one, as one, together" (cognates: Latin semel "once," similis "like;" see same).
sempiternal (adj.) Look up sempiternal at Dictionary.com
c.1400, from Old French sempiternel "eternal, everlasting" (13c.) or directly from Late Latin sempiternalis, from Latin sempiternus "everlasting," from semper "always, ever" (see semper-) + aeternus "eternal" (see eternal). Related: Sempiternally.
senate (n.) Look up senate at Dictionary.com
c.1200, "legal and administrative body of ancient Rome," from Old French senat or Latin senatus "highest council of the state in ancient Rome," literally "council of elders," from senex (genitive senis) "old man, old" (see senile). Attested from late 14c. in reference to governing bodies of free cities in Europe; of national governing bodies from 1550s; specific sense of upper house of U.S. legislature is recorded from 1775.
senator (n.) Look up senator at Dictionary.com
c.1200, "member of an (ancient) senate," from Old French senator (Modern French sénateur), from Latin senator "member of the senate," from senex "old; old man" (see senate). An Old English word for one was folcwita. As "member of a (modern) governing body" from late 14c.; specifically in U.S. use from 1788. Fem. form senatress attested from 1731. The Senators was the name of the professional baseball team in Washington, D.C., from 1891 to 1971.
senatorial (adj.) Look up senatorial at Dictionary.com
1740, from French sénatorial or from Latin senatorius "pertaining to a senator" or formed in English from senator + -al (1). Earlier adjectives were senatory (1520s), senatorian (1610). Related: Senatorially.
send (v.) Look up send at Dictionary.com
Old English sendan "send, send forth; throw, impel," from Proto-Germanic *sandijan (cognates: Old Saxon sendian, Old Norse and Old Frisian senda, Middle Low German and Middle Dutch senden, Dutch zenden, German senden, Gothic sandjan), causative form of base *sinþan, denoting "go, journey" (source of Old English sið "way, journey," Old Norse sinn, Gothic sinþs "going, walk, time"), from PIE root *sent- "to head for, go" (cognates: Lithuanian siusti "send;" see sense (n.)).

Also used in Old English of divine ordinance (as in godsend, from Old English sand "messenger, message," from Proto-Germanic *sandaz "that which is sent"). Slang sense of "to transport with emotion, delight" is recorded from 1932, in American English jazz slang.
send-off (n.) Look up send-off at Dictionary.com
"a farewell" (especially a funeral), 1872, from verbal phrase (attested by 1660s), from send (v.) + off (adv.).
send-up (n.) Look up send-up at Dictionary.com
"a spoof," British slang, 1958, from verbal phrase send up "to mock, make fun of" (1931), from send (v.) + up (adv.), perhaps a transferred sense of the public school term for "to send a boy to the headmaster" (usually for punishment), which is attested from 1821.
sended Look up sended at Dictionary.com
alternative past tense and past participle of send. Attested since late 14c.
sender (n.) Look up sender at Dictionary.com
c.1200, agent noun from send (v.). In 1930s slang, a popular musician or song. Sendee is recorded from 1806.
Seneca Look up Seneca at Dictionary.com
1610s, from Dutch Sennecas, collective name for the Iroquois tribes of what became upper New York, of uncertain origin, perhaps from a Mahican name for the Oneida or their village. Earlier sinnekens, senakees; form probably influenced by the name of the ancient Roman philosopher.
Senegal Look up Senegal at Dictionary.com
African nation, named for the river through it, perhaps from a local word meaning "navigable."