Preposition

preposition, in English, the part of speech embracing a small number of words used before nouns and pronouns to connect them to the preceding material, e.g., of, in, and about. Prepositions are a class that is typical of the structure of Indo-European languages, but similar classes are found in some other languages.

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Preposition 

a class of syncategorematic words or parts of speech. They are used in many languages, including Indo-European and Semitic, for the expression of various relationships between the dependent and principal members of a word combination. (The dependent member is usually a noun or pronoun.)

The preposition always precedes the dependent member. Functioning only in the role of a syntactic relation marker between the parts of a sentence, prepositions are not themselves members of a sentence. They are classed as primary or derived prepositions.

Primary prepositions are simple in composition and are distinguished by the multiplicity of relations that can be expressed by using them—for example, Russian bez, “without”; nad, “above”; v, “in”; k, “to”; or o, “about.” Derived prepositions are associated in structure and origin with autosemantic words. They may be adverbs (vblizi, “nearby”; navstrechu, “toward”; sboku, “from the side”), denominative prepositions (v oblasti, “in the field of; v tseliakh, “with a view to”), and deverbative prepositions (blagodaria, “(hanks to”; vkliuchaia, “including”).