Auxiliary and Modal Verbs
Modal verbs are auxiliary verbs in the sense that they allow subject-verb inversion and can be used with not in negative statements. However, auxiliary verbs such as do and does or the verb to be (e.g., to be going to do something) are used simply to conjugate the verb whereas modal verbs also add nuance to the meaning expressed by the verb.
For example, examine the following sentences:
1. Do you speak French?
2. Can you speak French?
In Sentence 1, do is an auxiliary verb used with speak to indicate the simple present tense.
Similarly, in Sentence 2, the modal verb can not only works as an auxiliary verb but also conveys the idea of an ability to perform the main verb (speak).
If you think the difference between Sentences 1 and 2 above is subtle, you are right. However, using a modal verbs can change the idea quite a bit depending on the context.
For example, compare the following sentences:
1. John eats breakfast every morning.
2. John must eat breakfast every morning.
3. John should eat breakfast every morning.
Sentence 1 has no modal verb; the verb eat simply expresses a habitual action.
The modal verb must in Sentence 2 expresses quite a different reality. It expresses the idea that eating breakfast is a necessity for John. Perhaps John does not feel well unless he eats breakfast, so he must do it every morning.
The modal verb should in Sentence 3 expresses the idea that eating breakfast is recommended for John. It appears that John does not eat breakfast every morning, but it would be a good idea if he did.
There is no one-to-one correspondence between a modal verb and the modality it expresses. The same modal verb can express more than one idea depending on how it is used.
For example, take the modal verb will. It can express the following ideas:
Promise/willingness: I’ll be there for you if you need me.
Decision: I’ll have the chicken salad, please.
Future certainty: The plane will on time.
Polite request: Will you please follow me.
Prediction: You will win the competition if you continue practicing.
Ability: The car won't start.
Repetitive action: He’ll always stutter when he lies.
Emphasis: I’m trying to help, but you won’t listen!
It should be stressed that differences in meaning quite often depend on the context in which the modal verb is used. “I will be there,” for example, could take on different meanings depending on the situation.
Types of Modal Verbs
Modal verbs are used as auxiliaries themselves. You use the modal verb in interrogative sentences by inverting it with the subject. To create a negative sentence, you simply add not to the modal verb.
John can swim very fast.
Can John swim very fast?
John cannot (can’t) swim very fast.
Semi-modal verbs work as modal verbs in the sense that they express a certain modality along with the main verb. However, they require an auxiliary verb to create interrogative and negative sentences whereas modal verbs work as auxiliary verbs themselves.
I need to come back tomorrow.
Do you need to come back tomorrow?
I don’t need to swim very fast.
Note that some semi-modal verbs (e.g., need) can also be used as an auxiliary verb, that is, without the need of another auxiliary.
Need I come back tomorrow?
You needn’t come back tomorrow.
Dare can also be used as a modal verb or as a non-modal verb:
Dare we say anything?
Do we dare (to) say anything?
We dared not say anything.
We didn’t dare (to) say anything.
Modal Verbs and Time of the Action or State
Continue the lesson on the next page to learn modal verbs and verb tenses.