in some languages, a relation or function word, as English in, by, for, with, to, etc., that connects a lexical word, usually a noun or pronoun, or a syntactic construction, to another element of the sentence, as to a verb (Ex.: he went to the store), to a noun (Ex.: the sound of loud music), or to an adjective (Ex.: good for her)
any construction of similar function (Ex.: in back of, equivalent to behind)