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prep·o·si·tion 1 (prĕpə-zĭshən)
n. Abbr. prep.
A word or phrase placed typically before a substantive and indicating the relation of that substantive to a verb, an adjective, or another substantive, as English at, by, with, from, and in regard to.

[Middle English preposicioun, from Old French preposicion, from Latin praepositiō, praepositiōn-, a putting before, preposition (translation of Greek prothesis), from praepositus, past participle of praepōnere, to put in front : prae-, pre- + pōnere, to put; see apo- in the Appendix of Indo-European roots.]

Usage Note: It was John Dryden who first promulgated the doctrine that a preposition may not be used at the end of a sentence, probably on the basis of a specious analogy to Latin. Grammarians in the 1700s refined the doctrine, and the rule became a venerated maxim of schoolroom grammar. There has been some retreat from this position in recent years, howeverwhat amounts to a recognition of the frequency with which prepositions end sentences in English. In fact, English syntax not only allows but sometimes even requires final placement of the preposition, as in We have much to be thankful for and That depends on what you believe in. Efforts to rewrite such sentences to place the preposition elsewhere can have stilted and even comical results, as is demonstrated in the saying (often attributed, probably falsely, to Winston Churchill) "This is the kind of pedantic nonsense up with which I will not put." · Even sticklers for the traditional rule can have no grounds for criticizing sentences such as I don't know where she will end up and It's the most curious book I've ever run across. In these examples, up and across are adverbs (or more properly, what linguists call particles), not prepositions. One sure sign that this is so is that these examples cannot be transformed into sentences with prepositional phrases. It is simply not grammatical English to say I don't know up where she will end and It's the most curious book across which I have ever run.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
pre·po·si·tion 2 also pre-po·si·tion (prēpə-zĭshən)
tr.v. pre·po·si·tioned, pre·po·si·tion·ing, pre·po·si·tions also pre-po·si·tioned or pre-po·si·tion·ing or pre-po·si·tions
To position or place in position in advance: artillery that was prepositioned at strategic points in the desert.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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