late 14c., "a quarter of a day, six hours," from Old French quadrant, cadran, name of a Roman coin, also "a sundial," from Latin quadrantem (nominative quadrans) "a fourth part, a quarter," also the name of a coin worth a quarter of an as; noun use of the present participle of quadrare "to make square; put in order, arrange, complete; run parallel, be exact," figuratively "to fit, suit, be proper," related to quadrus "a square," quattuor "four" (from PIE root *kwetwer- "four").

From 1570s as "the quarter of a circle, the arc of a circle containing 90 degrees." The ancient surveying instrument for measuring altitudes is so called from c. 1400, because it forms a quarter circle. Related: Quadrantal.

1847, "to drive into a corral," from corral (n.). From 1848 as "to form a circle with wagons." Meaning "to lay hold of, collar, capture, make a prisoner of" is U.S. slang from 1860. Related: Corralled.

1530s, "general course of instruction," from Modern Latin encyclopaedia (c. 1500), thought to be a false reading by Latin authors of Greek enkyklios paideia taken as "general education," but literally "training in a circle," i.e. the "circle" of arts and sciences, the essentials of a liberal education; from enkyklios "circular," also "general" (from en "in;" see in + kyklos "circle;" from PIE root *kwel- (1) "revolve, move round") + paideia "education, child-rearing," from pais (genitive paidos) "child" (see pedo-).

Modern sense of "reference work arranged alphabetically" is from 1640s, often applied specifically to the French Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts, et des Métiers (1751-65). Related: Encyclopedist.

"having a common center," c. 1400, from Old French concentrique, from Medieval Latin concentricus, from assimilated form of com "with, together" (see con-) + Latin centrum "circle, center" (see center (n.)).

1888 in yoga sense "a spiritual center of power in the human body," from Sanskrit cakra "circle, wheel," from PIE root *kwel- (1) "revolve, move round."

also chucker, chukka, "period in a polo game," 1898, from Hindi chakkar, from Sanskrit cakra "circle, wheel," from PIE root *kwel- (1) "revolve, move round."

"round, circular, spherical, having the shape of an orb," mid-15c., from Old French orbiculaire "round, circular," or directly from Late Latin orbicularis "circular, orbicular," from Latin orbiculus, diminutive of orbis "circle" (see orb). Related: Orbicularity.

instrument for making angular measurements in navigation or astronomy, 1731, from Late Latin octans "the eighth part," from octo "eight" (see octa-) on analogy of quadrant. In geometry, "the eighth part of a circle," by 1750.