The Probert Encyclopaedia of Architecture

LANTERN

In architecture a lantern is an open structure of light material set upon a roof, to give light and air to the interior. The term is also applied to a cage or open chamber of rich architecture, open below into the building or tower which it crowns; and to a smaller and secondary cupola crowning a larger one, for ornament, or to admit light; such as the lantern of the cupola of the Capitol at Washington DC, or that of the Florence cathedral.
Research Lantern