When we want to write about ‘ability’ we often use ‘can’ for the present and ‘could’ for the past. Using ‘to be able to’ is often more formal and complex, and is more likely to be correct than ‘can’. As you will see from the examples below, ‘to be able to’ can be used with present, past, future and conditional tenses and can be used with modal verbs like ‘should’ and ‘might’.
EXAMPLES (present tense)
- Many gifted linguists ARE ABLE TO speak a range of languages. However, the vast majority of us ARE UNABLE TO communicate in more than one or two.
- Parents SHOULD BE ABLE TO make their children behave well without using physical punishment.
- Schools MIGHT BE ABLE TO improve their pupils’ grades by making sure the children have a nutritious meal before the lessons start.
EXAMPLES (past tenses)
- As a child I WAS ABLE TO work quickly but UNABLE TO concentrate for long periods of time.
- Some fortunate individuals HAVE always BEEN ABLE TO paint. For them, art seems to be a natural talent. However, for most of us, becoming a competent artist requires dedication and commitment over a number of years.
- Older members of society, who USED TO BE ABLE TO participate fully and lead an active life, may now be frustrated as they find themselves having less energy to contribute.
- The government ought to have built more roads in the past. Experts SHOULD HAVE BEEN ABLE TO predict that the number of motor vehicles would increase substantially.
EXAMPLES (future and conditional tenses)
- It is predicted that by the year 2050 we WILL BE ABLE TO speak any language we want by simply downloading the relevant information to our brain. This idea is dismissed by others as being far-fetched.
- If I had more money, I WOULD BE ABLE TO afford a luxury holiday.
- If I HAD BEEN ABLE TO vote in the last election, I would certainly have supported the main opposition party.
It is not possible to use ‘can’ or ‘to be able/unable to’ in continuous tenses: It is incorrect to write: ‘I am being able to’ or ‘I was being able to’.