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In the grammar of English, the term ''do''-support (or ''do''-insertion) refers to the use of the auxiliary verb ''do'', including its inflected forms ''does'' and ''did'', to produce negated clauses and questions, as well as other constructions in which subject–auxiliary inversion is required. The verb "do" can be used as an auxiliary even in simple declarative sentences, where it usually serves to add emphasis, as in "I ''did'' shut the fridge." However in the negated and inverted clauses referred to above, it is used because the rules of English syntax permit these constructions only when an auxiliary is present. Apart from the verb "be", where, for example, "I am not" is used, it is not allowable (in Modern English) to add the negating word ''not'' to an ordinary finite lexical verb, as in '' *I know not'' – it can only be added to an auxiliary (or copular) verb, hence if there is no other auxiliary present when negation is required, the auxiliary ''do'' is used, to produce a form like ''I do not (don't) know.'' The same applies in clauses requiring inversion, including most questions – inversion must involve the subject and an auxiliary verb, so it is not possible to say '' *Know you him?''; grammatical rules require ''Do you know him?'' ''Do''-support is not used when there is already an auxiliary or copular verb present; nor is it used with non-finite verb forms (infinitives and participles). It is sometimes used with subjunctive forms. Furthermore the use of ''do'' as an auxiliary should be distinguished from the use of ''do'' as a normal lexical verb, as in ''They do their homework''. ==Common uses== ''Do''-support appears to accommodate a number of varying grammatical constructions, e.g. 1) question formation, 2) the appearance of the negation ''not'', and 3) negative inversion. These constructions often cannot occur without ''do''-support, or the presence of some other auxiliary verb. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Do-support」の詳細全文を読む スポンサード リンク
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