idioms — an expression whose meaning is not predictable from the usual meanings of its constituent elements, as kick the bucket or hang one's head, or from the general grammatical rules of a language, as the table round for the round table, and that is not a constituent of a larger expression of like characteristics.
syntaxes — Linguistics. the study of the rules for the formation of grammatical sentences in a language. the study of the patterns of formation of sentences and phrases from words. the rules or patterns so studied: English syntax. a presentation of these: a syntax of English. an instance of these: the syntax of a sentence.
