Etymology
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reverse (adj.)

c. 1300, "opposite, contrary in position or direction, turned backward," from Old French revers "reverse, cross, opposite" (13c.) and directly from Latin reversus, past participle of revertere "turn back, turn about, come back, return" (see revert). In reference to a gear mechanism enabling a vehicle to go backward without changing the rotation of the engine, by 1875. Reverse angle (shot, etc.) in film-making is from 1934. Reverse discrimination is attested from 1962, American English. Reverse dictionary, one in which the words are arranged alphabetically by last letter to first, is by 1954.

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inhibitor (n.)

1868 as a Scottish legal term; 1914 in biochemistry; agent noun in Latin form from inhibit. Form inhibiter is attested from 1610s.

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reverse (v.)

early 14c., reversen, (transitive), "change, alter" (a sense now obsolete); late 14c., "turn (someone or something) in an opposite direction, turn the other way, turn inside out," also in a general sense, "alter to the opposite;" from Old French reverser "reverse, turn around; roll, turn up" (12c.), from Late Latin reversare "turn about, turn back," frequentative of Latin revertere "turn back, turn about; come back, return" (see revert).

From c. 1400 as "turn (something) upside down;" from early 15c. as "go backward" (intransitive). Of judicial sentences, "set aside, make void," mid-15c. In mechanics, "cause to revolve or act in a contrary direction," by 1860; the sense of "put a motor vehicle in reverse gear" is by 1902. Related: Reversed; reversing.

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reverse (n.)

mid-14c., "that which is directly opposite or contrary" (of something), from reverse (adj.) or from Old French revers, reverse "the opposite, reverse," or directly from Latin reversus, past participle of revertere. The meaning "a defeat, a change of fortune for the worse" is from 1520s. In numismatics, "the back or inferior side of a coin, the side without the main device or inscription" is from 1620s. As "the reverse gear of an engine or motor vehicle" by 1900. As a type of sports play (originally rugby) it is recorded from 1921.

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retrovirus (n.)

1977, earlier retravirus (1974), from re(verse) tra(nscriptase) + connective -o- + virus. So called because it contains reverse transcriptase, an enzyme that uses RNA instead of DNA to encode genetic information, which reverses the usual pattern. Remodeled by influence of retro- "backwards."

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unlearn (v.)

mid-15c., from un- (2) "reverse, opposite of" + learn (v.).

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cytosine (n.)

crystalline base which is one of the constituents of nucleic acids, 1894, from German cytosin (1894), from cyto- "cell" + -ose + chemical suffix -ine (2). "The name cytosine (due to Kossel and Neumann) is misleading. Cytosine is not, like adenosine and guanosine, a nucleoside but the sugar-free base." [Flood]

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unclasp (v.)

1520s, from un- (2) "reverse, opposite of" + clasp (v.). Related: Unclasped; unclasping.

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unsheathe (v.)

late 14c., from un- (2) "reverse, opposite of" + sheathe (v.). Related: Unsheathed; unsheathing.

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