can or could
We use the modal can to make general statements about what is possible:
It can be very cold in winter. (= It is sometimes very cold in winter)You can easily lose your way in the dark. (= People often lose their way in the dark)
We use could as the past tense of can:
It could be very cold in winter. (=Sometimes it was very cold in winter.)
You could lose your way in the dark. (=People often lost their way in the dark)
You could lose your way in the dark. (=People often lost their way in the dark)
We use could to show that something is possible in the future, but not certain:
If we don’t hurry we could be late. (=Perhaps/Maybe we will be late)
We use could have to show that something is/was possible now or at some time in the past:
It’s ten o’clock. They could have arrived now.
They could have arrived hours ago.
They could have arrived hours ago.