Bay windows and bow windows are both types of window installations that protrude outward from the wall of a building, but they have distinct differences. Bay windows typically consist of three large panels of glass, with a fixed centre window and two smaller windows on either side that can be operable or fixed. On the other hand, bow windows usually have four or more windows, creating a curved appearance. The windows in a bow window are typically equal in size and can be operable or fixed.