auxiliary verb - definition and synonyms

noun [countable] linguistics 

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singularauxiliary verb
pluralauxiliary verbs or auxiliaries

or auxiliary 

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/ɔːɡˈzɪliəri/

  1. the verbs ‘be’, ‘do’, and ‘have’ in English, when they are used with another verb to form tenses, questions, question tags, and the passive. For example in the sentencesI am listening’, ‘Are you working?’, ‘You don’t like her, do you?’ and ‘The bill has been paid’, ‘am’, ‘are’, ‘do’, and ‘has been’ are all auxiliaries.
See also