Can or could

CAN or COULD | Ability

CAN is used to talk about the ability to do something at a given time in the present or future

Example:

He can speak Chinese fluently.

COULD is used to talk about past time

Example:

I could run 10 miles when I was young.

CAN or COULD | Request

COULD is used as a polite way of telling or asking someone to do something

Example:

Could you lock the door when you leave?

Can is more informal

Example:

Can you take me to the Victoria station?

CAN or COULD | Possibility

CAN is used to make general statements about what is possible

Example:

In Norway, temperatures can be low as -50°C in winter.

COULD is used to show that something is/was possible now or at specific event in the past

Example:

The weather station said temperaturescould be as low as -10°C tonight.

CAN or COULD | Asking Permission

CAN is used to ask for permission to do something in informal way

Example:

Can I borrow your car tomorrow?

Could is more formal and polite than can

Example:

Could I choose my own doctor?

CAN or COULD | Talking about things which are allowed

We use can to talk about things which are allowed in the present or future

Example:

You can take a holiday tomorrow if you want.

We use could to talk about things which are allowed in the past

Example:

When I first started this job we couldtake holiday when we wanted.