Traffic light: a signal that controls the traffic on a road, by means of red, orange and green lights that show when you must stop and when you can go Source
But many people say "stop light", but seem British means it "a red traffic light" & American means it "traffic light" or "brake light" (Source).
So, what is red traffic light?
But sometimes, people say "Go straight and then turn left at the light". So, "light" also means "traffic light"?