English has a big bagful of auxiliary verbs. You may have learned these as “helping verbs” in elementary and middle school, since they are sometimes described as verbs that “help” the main verb express its meaning. There are even schoolroom songs about them. They are a curious bunch.
The auxiliaries include the modal verbs (can and could, shall and should, will and would, may and might, and must). The verb that follows a modal is in its bare, uninflected form: can go, could go, must go, and so on. There are also a number of semi-modal auxiliary verbs (such as dare, need, ought to, had better, have to, and used to). Some are compound words spelled with a space and several have unusual grammatical properties as well, such as being resistant to contraction or inversion. And in parts of the English-speaking world, modals can double up, yielding expressions like might could, may can, might should, and more.
Aside from the modals, semi-modals, and double modals, the primary auxiliaries are forms of have, be, and do, which are inflected for tense (is versus was, has versus had, do versus did), number (is versus are, has versus have), and person(is versus am versus are, do versus does). These auxiliaries help to indicate verbal nuances like emphasis, the perfect and progressive aspects, and the passive voice. Here are some examples, adapted from Ernest Hemmingway’s The Old Man and the Sea:
Those who did catch sharks had taken them to the shark factory on the other side of the cove … (emphatic do and perfect aspect had)
The old man opened his eyes and for a moment he was coming back from a long way away. (progressive aspect)
His shirt was patched so many times that it was like the sail … (passive voice)
The primary auxiliaries come before the negative adverb not and allow contraction to it.
They didn’t catch sharks.
His shirt wasn’t patched.
He hadn’t taken the sharks.
And they play a role in questions by hopping to the left over the subject
Did they catch sharks?
Was his shirt patched?
Had he taken the sharks?
or by being copied at the end in a tag question.
They caught sharks, didn’t they?
His shirt was patched, wasn’t it?
He had taken the sharks, hadn’t he?
Main verbs like see and go and walk don’t do any of those tricks.
Things get even curiouser, however, because the helping verbs have and do have doppelgangers that actually are main verbs.
The old man did his chores.
His shirt had a tear in it.
How do we know these are main verbs and not helping verbs? Well, for one thing, they are the only verbs in the sentence. For another, they can occur with other helping verbs:
The old man had done his chores.
His shirt had had a tear in it all day.
And if you make the sentences questions or negate them, you have to add a form of auxiliary do.
Did the old man do his chores?
Did his shirt have a tear in it?
The helping verb be also has a doppelganger main verb, but the forms of main verb be behave pretty much just like the helping verb. More curious behavior, keeping us on our toes. The first sentence below has past tense main verb was followed by an adjective; the other two have the past tense helping verb was.
The shark was tenacious. (main verb was)
The shark was never caught. (auxiliary was)
The old man was trying his best. (auxiliary was)
But all three was forms hop to the left in questions.
Was the shark tenacious?
Was the shark ever caught?
Was the old man trying his best?
The curious behavior of helping verbs goes on and on, with different dialects doing different things. If you’ve read many British novels or watched British television you might have noticed forms of helping verb do popping up in elliptical sentences. Here’s an example from J. R. R. Tolkien’s The Two Towers: “Sam frowned. If he could have bored holes in Gollum with his eyes, he would have done.” (For a study of these forms, check out Ronald Butters’s 1983 article “Syntactic change in British English propredicates.”)
In African American English, the auxiliary done lends a completive meaning to events. You can see it in these dialogue examples from August Wilson’s Fences and from Walter Mosely’s Blond Faith: “Now I done give you everything I got to give you!” and “Didn’t she tell you that Pericles done passed on.” For more on this use of done, take a look at the chapters by Lisa J. Green and Walter Sistrunk and by Charles E. DeBose in the Oxford Handbook of African American Language.
We’ve just scratched the surface of auxiliaries. I hope you’ve become curious about these curious words.