Windows are made of four major components: stiles, sashes, muntins and glazing. Depending on its design and purpose, there may be other features on a particular window to suit the needs of a building or the preferences of a homeowner.
Stiles are the vertical supports of the window that run vertical to the window sash, a frame made of a top and bottom rail.
Muntins are any grid-like structures that bisect the glass of the window. These can be functional, supporting small, individual panes of glass, or decorative. Muntins can appear on the exterior of a pane or between panes.
Glazing is the glass component of a window made of one or more layers of glass. Double-glazing is an energy-efficient option as it traps air between the panes, providing a barrier to escaping heat.
When installed, the bottom of a window rests on an apron, a board built into the window's opening. In many cases the apron is bookended by a stool, a shelf that sticks out from the window opening. Jambs frame the window opening and are sized according to the measurements of the window. Casings cover the rough opening of the window opening and often provide a decorative element to a window.
Most windows employ some sort of opening mechanism, such as a latch or hand crank.