definition
strict definition
awning
An openable window hinged at the top of its frame, with the pane swinging about that upper edge.
An awning window is an openable window which swings on a hinge at the top of the frame. The window takes its name because it usually looks like an awning when it is open.
The upper edge supplies the hinge axis. A hopper window instead hinges at the bottom.
The name concerns the opening action of the pane. A separate awning mounted above another kind of window does not change that window's hinge arrangement.