Etymology
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role (n.)

c. 1600, "part or character one takes," from French rôle "part played by a person in life," literally "roll" (of paper) on which an actor's part is written, from Old French rolle (see roll (n.)). Not originally in English with direct reference to actors and the stage, but figurative of them. The meaning "any conspicuous function performed characteristically by someone" is by 1875. In the social psychology sense is from 1913. Role model, one taken by others as a model in performance of some role, is attested by 1957.

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theory (n.)

1590s, "conception, mental scheme," from Late Latin theoria (Jerome), from Greek theōria "contemplation, speculation; a looking at, viewing; a sight, show, spectacle, things looked at," from theōrein "to consider, speculate, look at," from theōros "spectator," from thea "a view" (see theater) + horan "to see," which is possibly from PIE root *wer- (3) "to perceive." Philosophy credits sense evolution in the Greek word to Pythagoras.

Earlier in this sense was theorical (n.), late 15c. Sense of "principles or methods of a science or art" (rather than its practice) is first recorded 1610s (as in music theory, which is the science of musical composition, apart from practice or performance). Sense of "an intelligible explanation based on observation and reasoning" is from 1630s.

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roleplay (n.)

also role-play, "act or condition of behaving as another would behave in a certain situation," 1958, from the verbal phrase, "to act out the role of" (by 1949); see role (n.) + play (v.). Related: Role-playing

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recast (v.)

also re-cast, c. 1600, "to throw again," from re- "back, again" + cast (v.). Sense of "to cast or form anew, remodel," especially of literary works and other writing, is from 1790. Meaning "compute anew" is by 1865. Theater sense of "assign an actor or role to another role or actor" is by 1951. Related: Recasting. As a noun, "a fresh molding, arrangement, or modification," by 1840.

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showgirl (n.)
"actress whose role is decorative rather than histrionic" [OED], 1836, from show (v.) + girl.
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theorist (n.)
"one given to theory and speculation," 1590s; see theory + -ist.
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theoretical (adj.)
1610s, "contemplative," with -al (1) + Late Latin theoreticus "of or pertaining to theory," from Greek theoretikos "contemplative, speculative, pertaining to theory" (by Aristotle contrasted to praktikos), from theoretos "that may be seen or considered," from theorein "to consider, look at" (see theory). Meaning "pertaining to theory, making deductions from theory not from fact" (opposed to practical) is from 1650s; earlier in this sense was theorical (c. 1500). Meaning "ideal, hypothetical" is from 1790s (implied in theoretically). Related: theoretician.
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rpg (n.)

by 1979, initialism (acronym) from role-playing game (see roleplay). As an initialism for rocket-propelled grenade, by 1970.

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incase (v.)

variant of encase.

Theory of Incasement, an old theory of reproduction which assumed that when the first animal of each species was created, the germs of all other individuals of the same species which were to come from it were incased in its ova. The discovery of spermatozoa developed the theory in two opposite directions: the ovulists, or ovists, held still to the theory of incasement in the female while the animalculists, or spermists, entertained the theory of incasement in the male. [Century Dictionary]
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magnetosphere (n.)

coined 1959, from magneto- + sphere. So called because it is the region around the earth (and some other planets) in which the magnetic field of the planet plays a dominant role in the motion of particles.

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