English verbs and verb phrases perform four primary and six nominal functions within English grammar. Auxiliary verbs, however, differ from prototypical verbs in that auxiliary verbs perform a limited set of grammatical functions. The auxiliary verbs in English include the modal verbs and quasi-modal verbs, the do-operator, perfect have, progressive be, and passive be. The five functions of the English auxiliary verbs are:
The following sections explain and exemplify the five grammatical functions of auxiliary verbs in English grammar.
Auxiliary Verbs as Modals
The first grammatical function that auxiliary verbs perform is the modal. A modal is a word that expresses modality. The auxiliary verbs that can function as modals include the modal verbs can, could, may, might, must, shall, should, will, and would and the quasi-modal verbs used to, ought to, had better (best), dare, and need. For example, the following italicized auxiliary verbs function as modals:
- My aunt can come to your party.
- You might want to bring a sweater.
- He should take off his muddy boots first.
- Will you please turn the oven on for me?
- I used to walk around town every night.
- She dare not arrive home after her curfew.
Note that the to and better (best) of the quasi-modal verbs function as particles. The verbs dare and need function as modals only within negated verb phrases and within subject-verb inversion of the verb phrase of interrogative sentences.
Auxiliary Verbs as Operators
The second grammatical function that auxiliary verbs perform is the operator. An operator is a word that facilitates the expression of negation, interrogatives, and emphasis. The auxiliary verb that can function as an operator is do, or the do-operator. For example, the following italicized auxiliary verbs function as operators:
- Do you want to attend the fair with me?
- Does she always wear neon green lipstick?
- Did he color inside the lines?
- Grandma does want us to come over on Sunday.
- I do love pumpkin cookies during the fall.
- We did travel to Germany last summer.
Auxiliary Verbs as Perfects
The third grammatical function that auxiliary verbs perform is the perfect. A perfect is a word that expresses the perfect aspect. The auxiliary verb that can function as a perfect is have. For example, the following italicized auxiliary verbs function as perfects:
- We have already eaten.
- The child has taken the entrance exam.
- Have you entered the contest yet?
- I had been washing the dishes when the doorbell rang.
- Had you watered the garden yet?
- My pumpkins had been eaten by rabbits and squirrels.
Auxiliary Verbs as Progressives
The fourth grammatical function that auxiliary verbs perform is the progressive. A progressive is a word that expresses the progressive aspect. The auxiliary verb that can function as a progressive is be. For example, the following italicized auxiliary verbs function as progressives:
- I am reading a new book series with my daughter.
- Are you cooking dinner tonight?
- She is washing her hands as we speak.
- Was he riding the train when the accident occurred?
- We were watching TV when the storm hit.
- The house would have been being painted at the time.
Auxiliary Verbs as Passives
The fifth grammatical function that auxiliary verbs perform is the passive. A passive is a word that expresses the passive voice. The auxiliary verb that can function as a passive is be. For example, the following italicized auxiliary verbs function as passives:
- The dog is fed daily by a dog sitter.
- We are taught by a wonderful professor.
- I am annoyed by obnoxious library patrons.
- The package was delivered on Tuesday.
- The clock had been accidentally broken by some neighborhood children.
- The sunflowers were watered on Sunday morning.
The five grammatical functions of auxiliary verbs in English grammar are modal, operator, perfect, progressive, and passive.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.