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.

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.