Modal Verbs: Can, Could, To Be Able To

Can

"Can" is one of the most commonly used modal verbs in English. It can be used to express ability or opportunity, to request or offer permission, and to show possibility or impossibility.

Examples:

• I can ride a horse. ability
• We can stay with my brother when we are in Paris. opportunity
• She cannot stay out after 10 PM. permission
• Can you hand me the stapler? request
• Any child can grow up to be president. possibility

Using "Can" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "can" behaves in different contexts.

Modal Use	Positive Forms 1. = Present 2. = Past 3. = Future	Negative Forms 1. = Present 2. = Past 3. = Future	You can also use:
can general ability	1. I can speak Chinese. 2. SHIFT TO "COULD" I could speak Chinese when I was a kid. 3. SHIFT TO "BE ABLE TO" I will be able to speak Chinese by the time I finish my course.	1. I can't speak Swahili. 2. SHIFT TO "COULD" I couldn't speak Swahili. 3. SHIFT TO "BE ABLE TO" I won't be able to speak Swahili.	be able to
can ability during a specific event	1. With a burst of adrenaline, people can pick up cars. 2. SHIFT TO "BE ABLE TO" With a sudden burst of adrenaline, he was able to lift the car off the child's leg. 3. SHIFT TO "BE ABLE TO" With a sudden burst of adrenaline, he will be able to lift the car.	1. Even with a burst of adrenaline, people can't pick up something that heavy. 2. SHIFT TO "BE ABLE TO" Even the weight lifter, couldn't lift the car off the child's leg. 3. SHIFT TO "BE ABLE TO" Even three men working together won't be able to lift the car.	be able to
can opportunity	1. I have some free time. I can help her now. 2. SHIFT TO "BE ABLE TO" I had some free time yesterday. I was able to help her at that time. 3. I'll have some free time tomorrow. I can help her then.	1. I don't have any time. I can't help her now. 2. SHIFT TO "BE ABLE TO" I didn't have time yesterday. I wasn't able to help her at that time. 3. I won't have any time later. I can't help her then.	be able to
can permission	1. I can drive Susan's car when she is out of town. 2. SHIFT TO "BE ALLOWED TO " I was allowed to drive Susan's car while she was out of town last week. 3. I can drive Susan's car while she is out of town next week.	1. I can't drive Susan's car when she is out of town. 2. SHIFT TO "BE ALLOWED TO " I wasn't allowed to drive Susan's car while she was out of town last week. 3. I can't drive Susan's car while she is out of town next week.	may
can request	Can I have a glass of water? Can you give me a lift to school? Requests usually refer to the near future.	Can't I have a glass of water? Can't you give me a lift to school? Requests usually refer to the near future.	could, may
can possibility, impossibility	Anyone can become rich and famous if they know the right people. Learning a language can be a real challenge. This use is usually a generalization or a supposition.	It can't cost more than a dollar or two. You can't be 45! I thought you were about 18 years old. This use is usually a generalization or a supposition.	could

Could
"Could" is used to express possibility or past ability as well as to make suggestions and requests. "Could" is also commonly used in conditional sentences as the conditional form of "can."

Examples:

• Extreme rain could cause the river to flood the city. possibility
• Nancy could ski like a pro by the age of 11. past ability
• You could see a movie or go out to dinner. suggestion
• Could I use your computer to email my boss? request
• We could go on the trip if I didn't have to work this weekend. conditional

Using "Could" in Present, Past, and Future

Most modal verbs behave quite irregularly in the past and the future. Study the chart below to learn how "could" behaves in different contexts.

Modal Use	Positive Forms 1. = Present 2. = Past 3. = Future	Negative Forms 1. = Present 2. = Past 3. = Future	You can also use:
could possibility	1. John could be the one who stole the money. 2. John could have been the one who stole the money. 3. John could go to jail for stealing the money.	1. Mary couldn't be the one who stole the money. 2. Mary couldn't have been the one who stole the money. 3. Mary couldn't possibly go to jail for the crime.	might, may
could conditional of can	1. If I had more time, I could travel around the world. 2. If I had had more time, I could have traveled around the world. 3. If I had more time this winter, I could travel around the world.	1. Even if I had more time, I couldn't travel around the world. 2. Even if I had had more time, I couldn't have traveled around the world. 3. Even if I had more time this winter, I couldn't travel around the world.
could suggestion	1. NO PRESENT FORM 2. You could have spent your vacation in Hawaii. 3. You could spend your vacation in Hawaii.	NO NEGATIVE FORMS
could past ability	I could run ten miles in my twenties. I could speak Chinese when I was a kid. "Could" cannot be used in positive sentences in which you describe a momentary or one-time ability. Yesterday, I could lift the couch by myself. Not Correct	I couldn't run more than a mile in my twenties. I couldn't speak Swahili. "Could" can be used in negative sentences in which you describe a momentary or one-time ability. Yesterday, I couldn't lift the couch by myself. Correct	be able to
could polite request	Could I have something to drink? Could I borrow your stapler? Requests usually refer to the near future.	Couldn't he come with us? Couldn't you help me with this for just a second? Requests usually refer to the near future.	can, may, might

Can I …? Can you …? Could I … Could you …? and so on.

The negative form is can’t in spoken English and cannot in written English.
We sometimes say cannot, but it is very emphatic.
The negative form of could is couldn’t in spoken English and could not in written English.
We sometimes say could not.
We use can and can’t :

• To talk about ability:

Maria can speak four languages.
I can’t swim, but my sister can.

• To say that something is possible or impossible:

Learning English can be difficult [= Learning English is sometimes difficult.]
Children can be very naughty [= Children are sometimes very naughty.]
It’s still light. It can’t be bedtime.

• For requests and refusals of requests

Can I go home now?
You can go whenever you like.
You can borrow the car today, but you can’t have it tomorrow.

• To offer to help someone:

Can I help you?
Can I carry that bag for you?

We use could and couldn’t as the past tense of can/can’t:

• To talk about ability:

I could run very fast when I was younger.
She couldn’t get a job anywhere.

• To say that something was possible or impossible:

Our teacher could be very strict when we were at school. [= Some teachers were very strict.]
People could starve in those days. [= People sometimes starved.]
You couldn’t use computers in the nineteenth century.

• To make a polite request:

Could I go now please?
Could you lend me a dictionary please?

• To make a polite offer:

Could I give you a lift?
I could carry that for you.

We use could have:

• to show that something is possible now or was possible at some time in the past:

It’s ten o’clock. They could have arrived now.
They could have arrived hours ago.

Exercises:

Elementary

Exercise1

Look at the pictures and choose the best answer.

Exercise2

Complete the sentences with can or can't.

Exercise3

Make negative sentences. Use the verbs in brackets.

Exercise4

Rewrite the sentences.

Exercise5

Make statements or questions.

Exercise6

Use the verbs can, may, must in positive or negative forms.

Exercise7

Rewrite the sentences.

Exercise8

Read the sentences and choose the correct response.

Exercise9

Choose the correct verb forms and complete the sentences.

Intermediate

Exercise1

Mix and match.

Exercise2

Requests, offers or possibility?

Exercise3

Put in order.

Exercise4

Rules and regulations.

Exercise5

The logical possibility.

Exercise6

Multiple choice.

Exercise7

Modal Auxiliary Verbs Game - Can, Must, Would - Basketball

Exercise8
When i was two.

Exercise9
Paraphrase

Exercise10
Complete the following sentences using the most appropriate forms of the verbs

Advanced

Exercise1

Fill in the blanks with can or can't and then check your answers below.

Exercise2
Mix and match.

Exercise3
Fill in the spaces with the right modal verbs.


Can - To Be Able To

'Can' is also used to express ability. Another form that can be used to express ability is 'to be able to'. Usually, either of these two forms can be used.

Examples:
I can play the piano. => I'm able to play the piano.
She can speak Spanish. => She's able to speak Spanish.

There is no future or perfect form of 'can'. Use 'to be able to' in both future and perfect tenses.

Examples:
Jack's been able to golf for three years.
I'll be able to speak Spanish when I finish the course.

Special Case of the Past Positive Form

When speaking about a specific (non-general) event in the past only 'to be able to' is used in the positive form. However, both 'can' and 'to be able to' are used in the past negative.

Examples:
I was able to get tickets for the concert. NOT I could get tickets for the concert.
I couldn't come last night. OR I wasn't able to come last night.
 
Exercises:
Elementary:
Exercise1
Mini-test. Create the sentences.

Exercise2
Choose the most appropriate answer for expressing ability.

Exercise3
Choose the most appropriate answer for expressing the idea specified in parentheses.

Intermediate:
Exercise1
"Have to - Be able to". Complete the sentences.

Exercise2
Fill in the blanks with can, can’t, could, couldn’t or was / wasn’t able to

Exercise3
Choose the correct form.

Exercise4
Write the phrases in brackets in their correct forms into the gaps.

Exercise5
Complete the sentences.

Exercise6
Test


Advanced:
Exercise1
Multiple choice.

Exercise2
Multiple choice.

Exercise3
Multiple choice.

Exercise4
Put the modal verbs into the right tense.

My Test

Key