A window is an opening in a wall, door or roof that allows the passage of light, sound, and air. The sash and frame are also referred to as a window.  Many windows may be opened, to allow ventilation, or closed, to exclude inclement weather. Windows often have a latch or similar mechanism to lock the window shut or to hold it open by various amounts.

Window come in many different shapes and sizes.  Windows types commonly include but are not limited to Double/Single hung, Casement, Awning, Hopper, Skylight, Fixed, Bow and Bay Windows.