English Grammar (Modal Verbs or Modal Auxiliaries): Lesson 2-CAN and COULD (with examples!)

The Differences Between CAN and COULD

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Please take a notebook and a pen to write down important information. You will thus be more active and will get more out of this post.

Moving forward, this is actually the second lesson in the modal verbs or modal auxiliaries series.

REMEMBER:

  • There are 9 modal verbs in English: Must, Can, Could, May, Might, Will, Would, Shall and Should.
  • Modal verbs are tools that help us to express modality. In fact, modals allow the speaker to express his or her point of view regarding an action, an event or a situation.
  • Modal verbs always remain the same no matter the subject and cannot be conjugated. Moreover, they do not have present and past participles. (I am canning go./ I have canned go.)
Can and Could (Lesson on Modal Verbs)

Step 1: Characteristics of CAN

  • We use CAN in the present tense. (E.g. I can swim.)
  • A verb stem always follows CAN. (E.g. He can dance very well.) The verb stem is also known as the base of a verb. You can find examples of verb stems in the dictionary.
  • We do not add ‘TO‘ after CAN. (E.g. She can to speak Spanish.)
  • CAN is able to replace auxiliary verbs such as DO and BE which help us to form questions. (E.g. How can I help you?)

Step 2: Examples of CAN in the Affirmative Form (+)

Expressing Possibility

Here, CAN refers to a situation that is likely to happen but is not certain.

  • He can come today.
  • She can succeed in her project.
  • You can become an English teacher one day. You never know!

Your Turn: Make 3 sentences in which you express possibility in the present using CAN.

Expressing Ability

In this case, CAN refers to something that someone is able to do.

  • He can swim.
  • My sister can ride a bike.
  • They can speak several languages.

Your Turn: Make 3 sentences in which you express ability in the present using CAN.

Giving Permission

We can also use CAN to tell someone that they are allowed to do something. CAN is less formal than MAY.

  • You can swim here.
  • They can stay in our house.
  • He can enter the room.

Your Turn: Make 3 sentences in which you give someone permission in the present using CAN.

Step 3: Examples of CAN in the Negative Form (-)

Expressing Impossibility

In this context, we use CAN + NOT to talk about something that is unlikely to happen. It is not certain.

  • He can’t come today. It’s raining.
  • She cannot become a politician one day. She is too honest.
  • We can’t be late. The bus is already here.

Your Turn: Make 3 sentences in which you express impossibility in the present using CAN + NOT.

Expressing Prohibition

This is another usage of CAN + NOT in which the subject does not have permission to do something.

  • She can’t go out. She’s grounded.
  • You can’t stay in this area. It’s protected.
  • They cannot smoke here. It is forbidden.

Your Turn: Make 3 sentences in which you express prohibition in the present using CAN + NOT.

Expressing Inability

This is when CAN + NOT are used to talk about something that someone is not able to do.

  • I can’t ski. I don’t know how to do this.
  • He can’t speak Japanese even though he has been trying for years.
  • We can’t sit still in class when the lesson is boring.

Your Turn: Make 3 sentences in which the subject expresses inability in the present using CAN + NOT.

Step 4: Examples of CAN in the Interrogative Form(?)

Asking for Permission

Here, we use CAN to ask somebody if we can do something.

  • Can I go to the bathroom, teacher?
  • Can we stay here? Is it allowed?
  • Can they leave their stuff here?

Your Turn: Make 3 sentences in which the subject asks for permission from someone in the present using CAN.

Asking Questions in Conditional Sentences

Here, we use CAN to ask WH- or Yes/NO questions in hypothetical or unreal situations.

  • What can I do if I feel sick on the plane?
  • Can I come if I bring some cake?
  • How can I write an essay on immigration if I don’t know anything about the subject?

Your Turn: Make 3 sentences in which the subject asks WH- or Yes/No questions in conditional sentences using CAN.

Asking for Information

In this case, CAN behaves like an auxiliary verb and helps us to form WH-questions.

  • What can I do to make you feel happy?
  • How can I help you?
  • When can I come?

Your Turn: Make 3 sentences in which the subject asks for information using CAN.

Making Requests

In this incident, the speaker can use CAN ???? to ask something from someone.

  • Can I call you today?
  • Jane, can you help me with my homework?
  • Can you come with me?

Your Turn: Make 3 sentences in which the subject makes a request using CAN.

Making Offers

It is also possible for you to use CAN to ask someone if you can do something for them.

  • Can I drive you to the airport?
  • Mum, can I help you with the dishes?
  • Can we mow your lawn, grandpa?

Your Turn: Make 3 sentences in which the subject makes an offer using CAN.

Can and Could (Lesson on Modal Verbs)

Step 5: Characteristics of COULD

  • We use COULD as the past tense of CAN. (E.g. I could speak Italian with my nanny when I was 5.)
  • We also use COULD in second conditionals. (E.g. If I had a lot of money, I could go to Malawi every month.) This past form of CAN is also called the unreal past because it refers to a an unreal or hypothetical situation. However, note that the action ‘go to Malawi‘ will happen in the future.
  • A verb stem always follows COULD. (E.g. He could dance very well.) The verb stem is also known as the base of a verb. You can find examples of verb stems in the dictionary.)
  • We do not add ‘TO‘ after COULD. (E.g. She could to speak Spanish.)
  • COULD is able to replace auxiliary verbs such as DO and BE which help us to form questions. (E.g. How could you do this to me?)

Step 6: Examples of COULD in the Affirmative Form (+)

Expressing Possibility in the Past

Here, COULD + HAVE–EN/ED (Present Perfect) refer to a situation that did not happen in the past but was likely to happen. Sometimes, this tone can be reproachful.

  • He could have come that day.
  • She could have succeeded in her project.
  • You could have become an English teacher.

Your Turn: Make 3 sentences in which you express possibility in the past using COULD + HAVE–EN/ED (Present Perfect).

Expressing Possibility in the Future

In this instance, COULD helps us to say that there is a chance that a situation can be realised in the future.

  • I could come tomorrow.
  • We could talk to him.
  • The train could arrive at any time.

Your Turn: Make 3 sentences in which you express possibility in the future using COULD.

Expressing Possibility in the Future in Conditional Sentences

In this case, we use COULD to refer to a hypothetical situation that is possible in the future, depending on the realisation of a previous action.

  • If they were rich, they could buy a mansion with a swimming pool.
  • I could stop living in the city, if I became famous.
  • If they talked to him, he could give them the solutions to their problems.

Your Turn: Make 3 sentences in which you express possibility in the future in conditional sentences using COULD.

Expressing Ability in the Past

In this case, COULD refers to something that someone was able to do in the past.

  • He could swim across that big river when he was sixteen.
  • My sister could ride a bike as soon as she was five.
  • In the past, people could communicate with each other using telephone booths.

Your Turn: Make 3 sentences in which you express ability in the past using COULD.

Gives Permission in the Past

We can equally use COULD to say that someone was allowed to do something in the past.

  • He could stay with us.
  • We could watch TV until late at night.
  • They could go to the cinema when they were ten.

Your Turn: Make 3 sentences in which we say that someone was allowed to do something in the past.

Step 7: Examples of COULD in the Negative Form (-)

Expressing Impossibility in the Past

In this context, we use COULD + NOT +HAVE-EN/ED (Present Perfect) to talk about something that was unlikely to happen in the past.

  • He couldn’t have done it. He was away at that time.
  • She couldn’t have written the letter. She was sick.
  • They couldn’t have changed their address. I saw their car yesterday.

Your Turn: Make 3 sentences in which you express impossibility in the past using COULD + NOT +HAVE-EN/ED (Present Perfect).

Expressing Impossibility in the Past in Third Conditionals

In this context, we use COULD + NOT +HAVE-EN/ED (Present Perfect) to talk about something that did not happen in the past but there was a possibility for its realisation if another action had been done.

  • He couldn’t have done it, if I had come after seven.
  • She couldn’t have stayed with him, if she hadn’t felt supported.
  • They couldn’t have won the game, if they had not listened to the coach’s advice.

Your Turn: Make 3 sentences in which you express impossibility in the past in third conditionals using COULD + NOT +HAVE-EN/ED (Present Perfect).

Expressing Prohibition in the Past

This is another usage of COULD + NOT in which the subject did not have the permission to do something in the past.

  • She couldn’t go out. She was grounded.
  • You couldn’t stay in that area. It was protected.
  • They could not smoke there. It was forbidden.

Your Turn: Make 3 sentences in which you express prohibition in the past using COULD + NOT.

Expressing Inability in the Past

This is when COULD + NOT are used to talk about something that someone was not able to do in the past.

  • I couldn’t speak for days.
  • He couldn’t eat after the operation.
  • We could not open the door despite our efforts.

Your Turn: Make 3 sentences in which you express inability in the past using COULD + NOT.

Step 8: Examples of COULD in the Interrogative Form(?)

Asking for Permission in a Polite Way

Here, we use COULD to ask somebody if we can do something in a civil or well-mannered way.

  • Could I go to the bathroom, teacher?
  • Could we stay here? Is it allowed?
  • Could they leave their stuff here?

Your Turn: Make 3 sentences in which the subject asks for permission from someone do something in a polite manner using COULD.

Asking Questions about Possibility

We can use COULD to ask questions about the likelihood of something happening. Here, it is almost as if the speaker were guessing.

  • What could be the reason of his silence?
  • Could this make you happy?
  • What could bring joy in your life?

Your Turn: Make 3 sentences in which the subject asks questions about possibility using COULD.

Asking questions in Conditional Sentences

In this case, we use COULD to form WH- and Yes/No questions in hypothetical or unreal situations.

  • How could I help you if you were very sick?
  • Could you write an essay about developing countries if you were asked to do it?
  • What could happen if the earth stopped revolving around the sun?

Your Turn: Make 3 sentences in which the subject asks for information in conditional sentences using COULD.

Making Polite Requests

In this incident, the speaker uses COULD to ask something from someone in a civil way.

  • Could I call you today?
  • Jane, could you help me with my homework?
  • Could you come with me?

Your Turn: Make 3 sentences in which the subject asks makes polite requests using COULD.

Making Polite Offers

It is also possible for you to use COULD to ask someone if you can do something for them. This is a more polite way of doing it.

  • Could I drive you to the airport?
  • Mum, could I help you with the dishes?
  • Could we mow your lawn, grandpa?

Your Turn: Make 3 sentences in which the subject makes polite offers using COULD.

Further Exploration:
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