My radiator in a bedroom is leaking water, what could be causing this?

Can you see where in the radiator it is coming from or attach a picture?

It is coming from the pipe that connects the radiator and the turn knob. Someone said it was the valve.

There is a lot of different valves out there. Most of them have a nut that goes around the valve stem, try to carefully tighten that nut to stop the leak.