northern circumpolar constellation, in Greek mythology queen of Ethiopia, wife of Cepheus and mother of Andromeda, from Latinized form of Greek Kassiepeia, Kassiopeia, a name of unknown etymology. A conspicuous "W" (or "M") of stars, always opposite the Big Dipper, she is represented as seated in a chair. The supernova there in 1572 outshone Venus, was observed by Tycho, among others, and helped revolutionize astronomy. Related: Cassiopeian.

1550s, "to return to a former state or place, go back," from Latin regressus "a return, retreat, a going back," noun use of past participle of regredi "to go back," from re- "back" (see re-) + gradi "to step, walk" (from PIE root *ghredh- "to walk, go").

In astronomy, "appear to move in a backward direction," by 1823. The psychological sense of "to return to an earlier stage of life" is attested from 1926. Related: Regressed; regressing.

old unit of liquid measure equal to one-third of a pipe (42 gallons), 1530s, from Anglo-French ters, Old French tierce (11c.). used in the sense "one-third" in various ways, from Latin tertia, fem. of tertius "a third," from PIE *tri-tyo-, from root *trei- (see three). Also used in Middle English for "a third part" (late 15c.), "the third hour of the canonical day" (ending at 9 a.m.), late 14c., and, in astronomy and geometry, "sixtieth part of a second of an arc."

1630s, in astronomy/astrology, "position of a heavenly body when it is on the meridian," from French culmination, noun of action from past participle stem of Late Latin culminare "to top, to crown," from Latin culmen (genitive culminis) "top, peak, summit, roof, gable," also used figuratively, contraction of columen "top, summit" (from PIE root *kel- (2) "to be prominent; hill"). Figurative sense of "highest point or summit" is from 1650s.

"one-sixtieth of a minute of degree," also "sixtieth part of a minute of time," late 14c. in geometry and astronomy, seconde, from Old French seconde, from Medieval Latin secunda, short for secunda pars minuta "second diminished part," the result of the second division of the hour by sixty (the first being the "prime minute," now simply the minute), from Latin secunda, fem. of secundus "following, next in time or order" (see second (adj.)).

The second hand of a clock, the pointer indicating the passage of seconds, is attested by 1759.

1580s, "one who cultivates one of the fine arts," from French artiste (14c.), from Italian artista, from Medieval Latin artista, from Latin ars (see art (n.)).

Originally especially of the arts presided over by the Muses (history, poetry, comedy, tragedy, music, dancing, astronomy), but also used 17c. for "one skilled in any art or craft" (including professors, surgeons, craftsmen, cooks). Since mid-18c. especially of "one who practices the arts of design or visual arts."

"arithmetic, music, geometry, astronomy" (the four branches of mathematics, according to the Pythagoreans), by 1751, from Latin quadrivium, which meant "place where four roads meet, crossroads," from quadri- "four" (from PIE root *kwetwer- "four") + via "way, road, channel, course" (see via). Compare liberal arts, and also see trivium.

The adjective quadrivial is attested from mid-15c. in English with the sense of "belonging to the quadrivium," late 15c. with the sense of "having four roads, having four ways meeting in a point."

late 14c., "one of the nine Muses of classical mythology," daughters of Zeus and Mnemosyne, protectors of the arts; from Old French Muse and directly from Latin Musa, from Greek Mousa, "the Muse," also "music, song," ultimately from PIE root *men- (1) "to think." Meaning "inspiring goddess of a particular poet" (with a lower-case m-) is from late 14c.

The traditional names and specialties of the nine Muses are: Calliope (epic poetry), Clio (history), Erato (love poetry, lyric art), Euterpe (music, especially flute), Melpomene (tragedy), Polymnia (hymns), Terpsichore (dance), Thalia (comedy), Urania (astronomy).

ancient constellation (representing Aesculapius), 1650s, from Latin, from Greek ophioukhos, literally "holding a serpent," from ophis "serpent" (see ophio-) + stem of ekhein "to hold, have, keep" (from PIE root *segh- "to hold").

Translated in Latin as Anguitenens and Serpentarius. Milton's "Ophiuchus huge in th' Arctick Sky" ("Paradise Lost") is a rare (minor) lapse for a poet who generally knew his astronomy; the constellation actually straddles the celestial equator, and, as its modern boundaries are drawn, dips into the zodiac: The sun passes through Ophiuchus from about Nov. 30 to Dec. 18. The serpent now is treated as a separate constellation.

"point at which the moon is farthest from the earth," 1590s, from French apogée or directly from Latin apogaeum, from Greek apogaion (diastema) "(distance) away from the earth," from apogaion, neuter adjective, "from land," here in a specialized sense "away from the earth," from apo "off, away" (see apo-) + gaia/ge "earth" (see Gaia).

The figurative sense of "climax, culmination" is from 1640s. A term from Ptolemaic astronomy, which regarded the earth as the center of the universe and applied the word to the sun and planets; for these bodies it was displaced in the Copernican system by aphelion. Adjective forms are apogeal, apogean, apogeic.