The study of fenestration (a fancy word for designing and arranging windows) involves a number of key terms that most homeowners may not know. Any primer on window terminology starts with identifying the parts of a window. Window performance and types also involve some new words and acronyms.

All windows, regardless of type, consist of glass panes, called glazing, that are secured within a four-part frame. The independent, framed glazing is called a sash. The vertical members of the sash are called stiles, and the horizontal pieces are the top rail and bottom rail. The sashes are installed within a framed opening trimmed by two side jambs, a head jamb, and a sill. How the sashes are installed and are opened and closed depends on the type of window.