Can / Could / Be able to - How and When to use

The focus of this lesson is to learn how and when to use the verbs can, could, be able to in sentences.

We will be looking at the meaning of these words, the purpose of using them in different contexts and the grammatical structure.

Can / Could / Be able to- meaning

These three verb forms have almost similar meanings. Basically they refer to “ability”, “being able to do something”. But the idea communicated may differ according to the context.

All the above sentences talk about my ability to perform an action. Therefore, the meaning is quite similar on the surface. However, there are slight differences in using these three verbs due to their indication of time and tone. Let’s analyze this in detail.

Can / Could / Be able to - Difference in usage in Sentences

Time

To talk about actions at different points of the timeline.

Tone

Meaning

Can / could : -

Can / could and Be able to - all these verbs can be used to talk about ability. Ability may refer to skills and talents.

When we use the verbs Can and Could, the ability we are referring to here is our ability in general terms. When you talk about your abilities in general, it means that you can do something in general , anywhere at any given time.

Be able to : -

Be able to is used to talk about a specific ability at a given point of time. Your ability here is limited to a specific time or specific location.

There is a specific reason preventing my general ability to swim. To indicate this difference, we may use “be able to” instead of “can / could”.

Grammatical Structure of Can/ Could

Can / Could

Can and Could are modal verbs. They belong to the closed class verbs category in English. They do not change according to the Subject, its number or person. They remain in their original form as always. Further, these modal verbs accompany only the base form of the main verb. They do not mix with other forms of the main verb.

The modal verbs are not sensitive to Number (Singular or plural) or person (1st, 2nd or 3rd person) of the subject.

Let’s develop sentences in the Present Tense using CAN : -

• I can sing.
• He can sing.
• She can sing.
• We can sing.
• You can sing.
• They can sing.

Let’s develop sentences in the Past Tense using COULD : -

• I could sing when I was young.
• He could sing when he was young.
• She could sing when she was young.
• We could sing when we were young.
• You could sing when you were young.
• They could sing when they were young.

We use Can and could to talk about general ability and use them in both positive and negative forms and also to ask questions as follows.

Present Tense - Can

- To talk about the abilities you have now.

Past Tense - Could

- To talk about the abilities you had in the past.

Negative Sentences with CANNOT and COULD NOT

Let’s Develop Negative Sentences with CANNOT : -

• I cannot speak English.
• He cannot speak English.
• She cannot speak English.
• We cannot speak English.
• You cannot speak English.
• They cannot speak English.

Let’s Develop Negative Sentences with COULD NOT : -

• I couldn’t speak English.
• He couldn’t speak English.
• She couldn’t speak English.
• We couldn’t speak English.
• You couldn’t speak English.
• They couldn’t speak English.

Questions with CAN / COULD

• Can I speak English ?
• Can he speak English ?
• Can she speak English ?
• Can we speak English ?
• Can you speak English ?
• Can they speak English ?
• Could I speak English ?
• Could he speak English ?
• Could she speak English ?
• Could we speak English ?
• Could you speak English ?
• Could they speak English ?

“Be Able to” in Sentences

This verb phrase has two important parts. First is the “be verb”. Be; “be verb” has to always agree with the subject and also should be in line with the time / tense. Therefore, “be” should be changed according to the subject and the Tense.

• Simple Present Tense - I am able to
• Simple Past Tense - I was able to
• Simple Future Tense - I will be able to
• Present Perfect Tense - I have been able to
• Past Perfect Tense - I had been able to
• Future Perfect Tense - I will have been able to

According to the Subject : -
eg:

• I am able to
• She is able to
• He is able to
• Rani is able to
• It is able to
• We are able to
• You are able to
• They are able to
• The children are able to

The be verb in “Be able to” changes according to the subject. Let’s understand this, using the verb in a sentence.

• I am able to sing today.
• She is able to sing today.
• They are able to sing today.

It also changes according to the time we are referring to. If I wish to talk about my ability in performing something yesterday, I could say;

Eg: I was not able to swim yesterday because I was not feeling well.

• Present - I am able to swim today because I am feeling better.
• Past - I was able to swim yesterday since I was feeling well.
• Future - I will be able to swim tomorrow since I’m feeling better today.

The verb phrase “ be able to” can be fixed in many situations whereas It is difficult to use “can “ and “could” in many grammatical structures.

Eg: Future Tense - Questions

Modal verbs cannot be changed into different structures. They are closed class verbs.They stay in the same form wherever they go. Therefore, when we cannot use a modal verb like “can” in a sentence due to its structure, “be able to” may be used.

Purpose - Using Can / Could to convey the opinion of the speaker.

Using CAN / COULD to talk about Possibility

Idea - Present and Future

Using CAN / COULD to make Requests

Using CAN / COULD to obtain Permission

Using CAN / COULD to make Suggestions

• A : We are getting late.
• B : We could take a taxi.

Remember to always refer to the context when understanding usage based on purpose. Consider the situation and the tone of the speaker to understand whether the sentence conveys an ability, suggestion, an offer, a request, a possibility or permission.