Corvus is a widely distributed genus of medium-sized to large birds in the family Corvidae. The genus includes species commonly known as crows, ravens, rooks and jackdaws; there is no consistent distinction between "crows" and "ravens", and these appellations have been assigned to different species chiefly on the basis of their size, crows generally being smaller than ravens. In Europe, the word "crow" is used to refer to the carrion crow or the hooded crow, while in North America, it is used for the American crow, fish crow, or the northwestern crow.