cross window

thumb|upright|Flamboyant Gothic building with cross-windows A cross-window is a window whose lights are defined by a mullion and a transom, forming a cross.

The Late Gothic cross-window is known since the 14th century and replaced the hitherto common Romanesque or Gothic arched window on buildings. Since then the latter have almost exclusively been reserved for church buildings. The two, upper lights were usually somewhat smaller than the two lower ones and could be opened separately. The latter is also true for a transom window, which has a horizontal bar or transom separating the lights.