What Are Modal and Semi-Modal Verbs? (C-Level, Advanced)
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Modal and semi-modal verbs are words or expressions that give more information and nuance to the verb. Essentially, in addition to expressing the idea in the verb, they express possibility, ability, permission, obligation, and so on.
Note. If you are looking for a more complete lesson on all modal and semi-modal verbs, see Modal Verbs in English (new tab) under “Verb Tense” Lessons.
Examples of Modal Verbs
Using CAN
”Can” Expressing Ability
In these examples, the modal verb “can” expresses ability or knowhow.
- Mary can speak 3 languages fluently.
- I can’t lift this box by myself. It’s too heavy.
- Can you solve this math equation?
”Can” Expressing Possibility
In the following sentences, “can” expresses a possibility for something to happen or be true:
- It can get very cold in winter here.
- Mistakes can happen if we rush.
- This medicine can cause drowsiness.
”Can” (Negative Form) Expressing Prohibition
In the negative form, “can” can also express prohibition:
- You can’t park here.
- You cannot use your smartphones during the test.
- Children cannot attend the play without adult supervision.
The negative “must not” (or “mustn’t”) aslo expresses prohibition, so you can also say,”You mustn’t park here,” “You must not use your smartphones during the test,” or “Children must noto attend the play without adult supervision.” Using “can” in this context is less formal than useing “must not.”
The above examples include only some of the meanings that “can” expresses in different contexts. (Yes, there are other possible meanings.) Other modal and semi-modal verbs (such as could, had better, may, might, need to, should, would, and so on) can also express multiple meanings.
Semi-Modal Verbs
Semi-modal verbs work just as modal verbs in the sense that they add nuance to the meaning of the main verb. Grammatically, however, they work just as other verbs, requiring an auxiliary verb to create interrogative and negative sentences whereas modal verbs work as auxiliary verbs themselves.
For example, notice the difference betwen the sentences below:
- We must leave leave by 7 tomorrow.
- We need to leave by 7 tomorrow.
- Do we need to leave by 7 tomorrow?
- We don’t need to leave by 7 tomorrow.
- We haven’t needed to leave by 7 in a long time.
”Must” is usually used in affirmative sentences and is quite formal. The semi-modal “need to” is more practical in that you can use it in affirmative, negative, and interrogative statements. Most importantly, as a semi-modal verb, it uses auxiliary verbs. In fact, it can even use other modal verbs with it:
- We may need to leave early next week.
- We shouldn’t have needed to leave so early last week.
Characteristics of Modal Verbs
Modal verbs have only one form when they are conjugated.
In the following examples, notice that the modal verbs do not have an -S in the third person.
Examples
I can
You can
She can
We can
They can
I must
You must
She must
We must
They must
Modal verbs do not use auxiliary verbs.
Most modal verbs do not use auxiliary verbs such as “do” or “did.” You simply use the modal verb for questions and negative sentences.
Examples
I can speak English.
I can’t speak English.
Can you speak English?
You may leave now.
You may not leave now.
May we leave now?
You should study hard.
You shouldn’t forget to study for the test.
Should we start studying now?
Most modal verbs Have only one or two forms.
Most modal verbs have only a present from and a past form. “Must” has only a present form.
can could
may might
must —
shall should
will would
For example, “must” has only a present form. However, it can express different verb tenses and ideas such as a fact or a future necessity:
I must start work at 9 every morning. (fact)
I must leave at 7 tomorrow. (future)
To express other verb tenses, you must use other constructions. For example, you can use have to in many verb tenses to express must.
I had to start work at 8 yesterday. (past)
Next week, we will have to study for the exam. (future with will)
Modal verbs are usually followed by the bare infinitive.
A bare infinitive is an infinitive without “to.” Many modal verbs use the bare infinitive, but not all of them do.
Examples
My brother can speak five languages.
We must finish in 10 minutes.
May I ask you a question?
Exception: Semi-modal verbs
Semi-modal verbs have different forms and use auxiliary verbs.
Semi-modal verbs (for example, have to, need to, be able to) express similar meanings to other modal verbs (for example, have to = must), but they work like ordinary verbs.
Semi-modals have various forms (for example, need, needs, needed, needing) and use auxiliary verbs for interrogative and negative sentences (doesn’t need to, will be needing to, didn’t need to, is going to need to).
Also notice that these semi-modal verbs are followed by a to-infinitive.
Example: MUST = HAVE TO
I must go.
I’m going to have to go tomorrow.
Do you have to go now?
I don’t have to go.
Example: CAN = BE ABLE TO
We can understand the teacher.
We will be able to understand the teacher next class.
Are you going to be able to understand the teacher next week?
No, we probably won’t able to understand the teacher.
Mastering Modal Verbs
What makes modal and semi-modal verbs challenging for English-language learners is that each of them can express different ideas. Sometimes these differences are subtle, yet they are important.
It is crucial to pay very close attention to how a modal verb is used in a particular context so that you can understand exactly what it expresses.
If you learn that a modal verb expresses an idea, do not assume that it does so every time you come across that modal verb. Rely on the context (i.e., a particular conversation or text about a particular topic) to understand which meaning makes sense.
Needless to say, you also need a great deal of practice. Read and listen to a variety of materials on a variety of topics. Engage in conversations about various subjects. The more you practice the language, the more likely you are to come across different uses of modal and semi-modal verbs.
Related Lesson
Modal Verbs in English (new tab). A more complete lesson on modal and semi-modal verbs, including a list of modal and semi-modal verbs and their meanings.