A preposition is a word placed before a noun or pronoun to form a phrase modifying another word in the sentence. Therefore a preposition is always part of a prepositional phrase. The prepositional phrase almost always functions as an adjective or as an adverb.

prepositions (2): after particular words and expressions
It is not always easy to know which preposition to use after a particular noun, verb or adjective. Here are some of the most common combinations...
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above and over
1 ‘higher than’: above or over Above and over can both mean ‘higher than’. Above is more common with this meaning.The water came up...
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prepositions (4): expressions without prepositions
This is a list of some common expressions in which we do not use prepositions, or can leave them out.discuss, enter, marry, lack, resemble and...
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prepositions (6): before conjunctions
Prepositions can be followed by conjunctions in some cases but not in others.indirect speech: prepositions dropped before thatPrepositions are not...
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across, over and through
on/to the other side of (line): across and overAcross and over can both be used to mean ‘on or to the other side of a line, river, road, bridge...
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