A key distinction in the word class of verbs is between main verbs (also called lexical verbs) and auxiliary verbs:
These semantic descriptions are a great starting point, particularly for younger children, but older children can use more sophisticated approaches to identifying auxiliary verbs.
First, auxiliary verbs are a closed class, which means that there is a limited number of them. Unlike main verbs, auxiliary verbs can be listed relatively easily.
Here are some examples of auxiliary verbs in sentences:
You can see that the auxiliary verbs come before the main verbs that they are helping. (The main verbs here are called and wondering.)
One important role of some auxiliary verbs, the aspectual auxiliaries be and have, is to express the notion of temporal aspect: whether an event or action expressed by a verb is ongoing or completed.
For example:
Other auxiliary verbs include do, and modal auxiliary verbs like can and should:
Auxiliary verbs share a number of characteristics referred to by the acronym NICE:
Negation
Auxiliary verbs take not or n’t to form negatives:
In fact, if there isn't an auxiliary in a sentence, one must be added to make the sentence negative.
Inversion
Auxiliary verbs are inverted with the Subject of the sentence to form questions.
Code
Sometimes a shorthand – a kind of 'code' – can be used with auxiliaries. This happens when the main verb is left out if it has been used already:
Emphasis
Auxiliaries can also be used to add emphasis.
The verbs be, have and do can be main verbs or auxiliary verbs. We can see this by comparing some examples.
In the next three examples they are main verbs (is, have and did are the only verbs here):
whereas in these examples they are auxiliaries helping other verbs: