English grammar (See all our English grammar tips)
CanThe auxiliary verb can means 'to be able to'. It allows us to express:
I can swim. I am able to swim. (or I know how to swim.)
This place can be dangerous. This place has the potential to be dangerous.
It can't be him. It's not possible that it's him.
• Permission, in informal language (may is the formal equivalent):
Can I leave now? Will you let me leave now?
• In the past and other perfect tenses (present perfect, past perfect, etc), could or was/were able to is used:
I couldn't finish the report before the deadline. I was not able to finish the report before the deadline.
• In the future will be able to is used:
By the end of the year, he'll be able to speak fluently. By the end of the year, he will have the ability to speak fluently.
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