Modals of Ability: Can, Could, Be able to, May, Might


These five verbs are examples of modal verbs.

  • can
  • could
  • be able to
  • may
  • might

Modal verbs are helping/auxiliary verbs that express ideas like ability, permission, possibility, and necessity. Many modal verbs have more than one meaning. They are always followed by the simple form of a verb. For example,

Alan can swim well.

This shows that Alan has the ability to swim.

1. Modals for Ability

Let’s start with expressing ability! We use can, be able to and could to show that someone has (or doesn’t have) an ability to do something.

Look at these examples:

Present/Future Ability Negative Past Ability Negative
Alan can swim well. Jackie cannot play piano. Paul could speak Chinese when he was a child. Mary couldn’t finish her homework last night.
I can meet you after school. We can’t visit Vancouver this weekend. Last night, there were no clouds in the sky and they could see all the stars. You couldn’t find the website this morning, could you?
I am able to speak two languages. I am not able to speak Arabic. When I was a young child, I wasn’t able to tie my shoes. I wasn’t able to finish my test yesterday.
Brenda is able to run quickly. Stacey isn’t able to finish a marathon. Shaun was able to complete the assignment. Paula wasn’t able to pass the class.
You are able to program a computer. We aren’t able to make a reservation tonight. They were able to catch six fish on their trip. You weren’t able to understand the answer, were you?

Did you notice that the verbs after “can/could/be able to” are always in the simple form? For example:

Alan can swim well.    (subject + auxiliary verb + simple verb + ...)

Do NOT change the modal auxiliary OR the main verb for he/she/it subjects. In addition, do not add “ing” or “ed”.

Alan can swims well. arrrow to the right Wrong!

Alan can to swim well. arrrow to the right Wrong!

Alan can swimming well. arrrow to the right Wrong!

Alan could swam well. arrrow to the right Wrong!

How can we make questions about ability? It’s easy!

Modal auxiliary + subject + main verb + ... ?

Can she play guitar?
Could you speak English when you were a child?

BE + subject + able to + main verb + ... ?

Are you able to understand the homework?
Were you able to finish the test?
Was he able to pass the exam?

Notice that we do not need the verbs “do/does/did” when we make questions!
The modal verb “be able to” includes the word “to”; the “to” is not an infinitive.

2. Modals for Possibility

Let’s learn about expressing possibility now.

The verbs may, might and could show possibility now and in the future. In this case, they have the same meaning.

Look at this conversation:

A: My mother said that it may snow tomorrow.

B: Really? It might snow?! That’s great! I could make a snowman or go for a “snow” walk.

A: Don’t get too excited. If the temperature is high, it may not snow. It may rain.

B: Well, I guess I could still go for a walk in the rain.

Be careful with may + “be” and “maybe”. Compare these sentences. Both are correct.

Ann is not here today. She may be sick. arrrow to the right “may be” is a modal.
Ann is not here today. Maybe she is sick. arrrow to the right “Maybe” is an adverb.

3. Modals for Permission

Finally, let’s look at ways to ask for and give permission. We use may, could and can to do this.

Formality Example
most formal/polite May I go to the washroom?
*only used with “I” and “we”
medium formal Could I borrow your dictionary?
Could he pay you tomorrow?
casual Can I call you back later?
Can she have a cookie?

Now, look at the (main) verbs that come after the subject. They are always in the simple form, just as with other modal verbs.

Again, the most polite/formal way to answer these questions is with “may.”


May I go to the washroom? Yes, you may (go to the washroom).
Yes, you can.
No, you may not.
No, you cannot.
Can she have a cookie? Yes, she can. No, she can’t.

Notice that we do not “contract” may + not = mayn’t. arrrow to the right Wrong!
Can’t and couldn’t are common contractions, however.

When you are sure that you understand the lesson, you can continue with the exercises.