auxiliaryverb

An auxiliary verb, or helping verb, is a verb that combines with a main verb to express grammatical information such as tense, aspect, voice, mood, or emphasis. Auxiliaries enable complex verbal constructions and appear in many languages, including English, where they help shape how an action relates to time, reality, or modality.

In English, the primary auxiliaries are be, have, and do. Be is used for continuous (progressive) aspect, as in I am studying, and for forming passive voice, as in The ball was thrown. Have forms the perfect aspect, as in She has finished, and can combine with other auxiliaries for more complex meanings (They have been waiting). Do serves as a support for question formation and negation in simple tenses (Do you like it? I do not know).

Modal verbs—can, could, may, might, shall, should, will, would, must—function as auxiliary verbs to express possibility, ability, necessity, or permission: They can swim; You must go; We should see it. Auxiliaries can be stacked to convey multiple layers of meaning, as in I have been waiting or They might have been studying.

Outside English, auxiliary verbs serve similar roles in marking tense, aspect, voice, or mood, though the specific forms and how they attach to main verbs vary by language. Some languages use auxiliary structures extensively, while others rely more on verbal inflection. The term distinguishes these helping verbs from the main lexical verb, which carries the core semantic content of the action.