Casement Window

A combination of frame, sash, weather-strip, concealed hinges and operating device assembled as a complete and properly operating unit. Casements have a flat sill and a sub-sill; screens and/or energy panels are optional. Operating casements have a crank handle for smooth operation.

See also Awning Window

Casement_window (Wikipedia)
Casement window, with latticed lights

A casement is a window that is attached to its frame by one or more hinges at the side. They are used singly or in pairs within a common frame, in which case they are hinged on the outside. Casement windows are often held open using a casement stay. Windows hinged at the top are referred to as awning windows, and ones hinged at the bottom are called hoppers.