Ability: Can could be able to

Ability: Can could be able to. What is the difference between the verbs ‘to be able to’ and ‘can’? This is what we will address in this post. But remember, we are only focusing on ‘ability’.

CAN / COULD / BE ABLE TO – WHAT’S THE DIFFERENCE?

‘Can‘ and ‘could‘ are auxiliary verbs. This means that they are minor verbs that support the main verb.
‘Be able to‘ is NOT an auxiliary verb.
‘Can‘ is only used to express ability in the present tense
‘Could‘ is only used to express ability in the past tense
‘Be able to‘ can be used in all tenses, but sometimes it is seen as a more formal option (particularly in the present tense)

PRESENT TENSE

‘Can’ is only used in the present tense when speaking about ability. ‘Be able to’ can be used in every tense, however it is much more common to use ‘can’ in the present tense.

To use ‘can’ in the present tense:

Use Subject + auxiliary verb ‘can’ (not) + main verb to show you have the ability to do something in the present tense:
- I can type 55 words per minute.
- Joe can’t come in to work today.
- Can you speak other languages?

To use ‘be (not) able to’ in the present tense:

Use Subject + am/are (not) able to + infinitive verb (without to) to also show you have the ability to do something in the present tense.
This is a more formal option. Can is more common.
- I am able to write 55 words per minute.
- Joe isn’t able to come to work today?
- Are you able to speak other languages?

PAST TENSE

Could is only used in the past simple tense when speaking about ability. Be able to is often used as well.

To use ‘could’ in the affirmative past tense:

Use subject + auxiliary verb ‘could’ + the main verb to talk about general ability to do something in the past.
- When I was younger I could work longer hours.
- My dad could fix anything when we were young.

To use was/were able to in the affirmative past tense:

Use subject + was/were able to + infinitive verb (without to) to talk about a specific ability in the past.
- I was able to speak to Martha this morning about the report.
- They were able to arrive on time to the dinner.

Use couldn’t or was/weren’t able to to show past inability:

Subject + couldn’t + main verb
Subject + was/weren’t able to + infinitve verb (without to)
- She couldn’t speak English when she started working here.
- She wasn’t able to speak English when she started working here.

OTHER VERB TENSES

FUTURE TENSE

Although the appropriate way to speak about the future tense is to use ‘be able to’, you will often here native speakers using the word ‘can’.

Can you meet with me tomorrow? (less formal, more commonly used)
Will you be able to meet with me tomorrow? (more formal)
Next week I am free and can meet whenever you want. (less formal, more commonly used)
Next week I am free and will be am able to meet whenever you would like. (more formal)

ALL OTHER TENSES

‘be able to’ in other tenses:

Present Continuous for future arrangements
- I am going to be able to go to the party.
Past Continuous
- I wasn’t going to be able to sing, but my throat is much better now.
Present Perfect
- We have been able to make lots of new friends.
Past Perfect
- She had been able to speak Spanish by the time they arrived in Spain.
Conditional
- If it doesn’t rain later, I will be able to meet you in front of the library at 6PM.
Future
- Daniel will not be able to attend the meeting tomorrow evening.

Common mistakes

Some of the most common mistakes are as follows:

Remember that can and could are not followed by ‘to’
- I can to call you later.
- I can call you later.
- Could you to come home early?
- Could you come home early?
Do not use ‘can’ or ‘could’ after a modal verb
- She might ~~can~~ come later.
- She might be able to come later.
- He should ~~could~~ be here.
- He should be able to be here.
‘Be able to’ can be very formal, so if you are talking with friends or even colleagues, this may sound too formal:
- Are you able to join me for lunch? (this sounds like a very formal invitation. Someone may laugh because it does not sound natural)
- Can you join me for lunch?
- Laura is able to swim. (it sounds like you are surprised by this fact. It’s way to formal.)
- Laura can swim.