An auxiliary verb (often known pedagogically as a helping verb) is a finite verb used to '’support a main verb, which it licenses as a bare infinitive.
Auxiliary verbs have NICE properties.
They can be classified into the primary auxiliary verbs and the modal auxiliary verbs.
- The primary auxiliary verbs are be, do and have.
- The modal auxiliary verbs (or modal verbs) are '’shall, '’should; will, would; can, could; may, might; and must.
- The semi-modal verbs need and [dare]] may be used as auxiliaries, although this is not common in contemporary English.
An English clause typically uses one or two auxiliary verbs, but up to three can be used, for example in I could have been a star.
Clauses using independent verbs do not have auxiliary verbs; this only applies to the present simple. A standalone verb is its own auxiliary; be, but sometimes have as well.