Collins Cobuild

participle.
When will I be able to pick them up?
He had been unable to get a ticket.
6
You use ‘used to be able to’ to say that something was possible in the
past, but is not possible now.
Everyone used to be able to have free eye tests.
You used to be able to buy cigarettes in packs of five.
7
 Note  that  you  also  use  ‘could’  followed  by  a  negative  word  and  the
comparative form of an adjective to emphasize a quality that someone
or something has. For example, if you say ‘I couldn’t be happier’, you
mean  that  you  are  very  happy  indeed  and  cannot  imagine  being
happier than you are now.
You couldn’t be more wrong.
He could hardly have felt more ashamed of himself.

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