Let's take a look at the different uses of could.
Possibility
Simon could be studying English right now. (present)
Simon could have studied English in Malta. (past)
Simon could go back to Malta next year. (future)
Conditional form of can
If I had more money, I could buy a new computer. (present)
If I had had more money, I could have bought a new computer. (past)
If I had more money this year, I could buy a new computer.(future)
Suggestion
No present form
You could have borrowed my car. (past)
You could borrow my car. (future)
Past ability
I could speak better French when I was younger.
Request
Could you give me a hand please?
Now try this could quiz:
