Ability: 'be able to'
A2 ElementaryThe phrase 'be able to' describes ability or possibility. It functions similarly to 'can' but allows for more flexibility across different tenses.
Overview
The structure be able to expresses the ability to perform an action. While it shares the same meaning as can in the present tense, it is often used to sound more formal or to express ability in tenses where can is grammatically impossible, such as the future or the present perfect.
Form
subject + be (am/is/are/was/were) + able to + verb
The verb be must be conjugated to match the subject and the tense. It is followed by able to and the base form of the main verb.
Examples
Can vs. Be able to
Use can for general ability in the present. Use be able to when you need to use a future or perfect construction.
| Feature | Can | Be able to |
|---|---|---|
| Tense | Present and Past (could) only | All tenses (Future, Perfect, etc.) |
| Formality | General / Informal | Slightly more formal |
Common mistakes
I will can help you tomorrow.
I will be able to help you tomorrow.
The modal 'can' does not have a future form; 'be able to' must be used instead.
He is able to swimming.
He is able to swim.
Always use the base form of the verb after 'to', not the -ing form.
Practice
Change this sentence to the future: 'I can swim.'
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I will be able to swim.
Answer:I will be able to swim.
Why:Because 'can' has no future form, we use 'will' followed by 'be able to'.
Complete the sentence: 'They ___ (not / be) able to find the keys yesterday.'
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were not / weren't
Answer:were not / weren't
Why:The sentence refers to the past, so the verb 'be' must be conjugated as 'were' to match the plural subject 'they'.
Is 'She is able to drive' more or less formal than 'She can drive'?
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More formal
Answer:More formal
Why:'Be able to' is generally considered more formal than the modal verb 'can'.