The principal parts of a window are the following:
Drip cap"A separate piece of wood projecting over the
top of the window; a component of the window casing.
The drip cap protects against moisture.
Window trough"The cut or groove in which the sash of
the window slides or rests.
Window sill"The shelf on the bottom edge of a
window, either a projecting part of the window frame or
the bottom of the wall recess that the window fits into. The
sill contains the trough and protects against moisture.
Windows 
