in grammar, this refers to the reversal of the usual order of subject and auxiliary verb in a declarative sentence. This creates a question so that, for example, The poodle is barking becomes: Is the poodle barking? Such constructions are of major interest in generative grammar and psycholinguistics areas. See also interrogative.
AUXILIARY INVERSION: "A person using an auxiliary inversion would change the sentence The dog is sitting, to Is the dog sitting?"