A window that projects outward from the wall surface to form a small alcove is called:

Explanation:

Bay windows 

• Bay windows project outside the external walls of a room.
• This projection may be triangular, circular, rectangular or polygonal in plan. Such a window is provided to get an increased area of opening for admitting more light and air.

Additional Information

Double Hung Pivoted Window 

• This type of window consists of a pair of shutters arranged one above the other which can slide vertically within the grooves provided in the frame.
• A pair of metal weights connected by a chain passing over pulleys is provided for each shutter. By this arrangement, the window can be opened at the top or bottom to the desired extent by pulling the metal weight suitably.
• Thus in this type of window, it is possible to have controlled ventilation. In addition, the shutter can also be cleaned easily.

Casement window

• Windows, where shutters open like doors, are called casement windows.
• The window has a frame which is rebated to receive the shutters.
• The shutters consist of style, top rail, bottom rail and intermediate rail, thus dividing it into panels. 

Clerestorey Window

• These windows are provided near the top of the main roof. The pivoted windows are used for this purpose.
• The clerestorey windows provide ventilation to the inside of the room where the front is blocked by veranda and improved the appearance of the building.