English auxiliary verbs are a small set of English verbs, which include the English modal auxiliary verbs and a few others. Although the auxiliary verbs of English are widely believed to lack inherent semantic meaning and instead to modify the meaning of the verbs they accompany, they are nowadays classed by linguists as auxiliary on the basis not of semantic but of grammatical properties: among these, that they invert with their subjects in interrogative main clauses and are negated either by the simple addition of not or by negative inflection.