verb + verb: auxiliary verbs
The need for auxiliary verbs
In English sentences, a lot of important meanings are expressed by the verb phrase—for example questioning, negation, time, completion, continuation, repetition, willingness, possibility, obligation. But English verbs do not have many different one-word forms: the maximum (except for be) is five (e.g. see, sees, seeing, saw, seen). So to express all these meanings, ‘auxiliary’ (or ‘helping’) verbs are added to other verbs. There are two groups.
be, do and have
Be is added to other verbs to make progressive and passive forms.
- Is it raining?
- She was imprisoned by a military court.
Do is used to make questions, negatives and emphatic forms of non-auxiliary verbs.
- Do you smoke?
- It didn’t matter.
- Do come in.
Have is used to make perfect forms.
- What have you done?
- I realised that I hadn’t turned the lights off.
For details, see be, have and do.
Modal auxiliary verbs
The verbs will, shall, would, should, can, could, may, might, must and ought are usually called ‘modal auxiliary verbs’. They are used with other verbs to add various meanings, mostly to do with certainty or obligation.
- She may be in Mexico.
- You must call Uncle Arthur.
For details, Modal auxiliary verbs.
Other verb + verb structures
Other verbs (e.g. seem) which are used in verb + verb structures are not usually called ‘auxiliary verbs’. One important difference is grammatical. In auxiliary verb structures, questions and negatives are made without do; in other verb + verb structures the auxiliary do has to be added to the first verb. Compare:
- She should understand.
Should she understand? - She seems to understand.
Does she seem to understand? - He is swimming.
He is not swimming - He likes swimming.
He doesn’t like swimming.
For more about these structures, see here.