Window Terminology

Short glossary of commonly used design terms in the window industry

If you are unsure on how to describe the style of window you require, then download our Window Terminology Guidance document here or read it now below.

The diagram below (Fig 1.0) shows four window panes in one frame. Three of the frames are contained in their own ‘sash’ to allow opening (grey area). The fourth is a fixed pane with no sash.

window terminology


Window Naming
1. Top Light or Fan Light Opening window with sash
2. Casement or Side hung window with sash
3. Fixed window pane
4. Top Hung or push out opening window with sash

Component Terminology
A. Frame (white area)
B. Jamb (left or right frame section)
C. Sill
D. Mullion (vertical strut within the frame)
E. Head
F. Transom (not shown – horizontal strut within frame)

Specifying the Opening
Opening (or ‘handing’) of the window is specified by the use of an arrow head or ‘V’ shape. The point of the arrow or (bottom of the ‘V’) denotes which side the hinges will be. The open end of the arrow (or ‘V’) denotes the position of the handle(s).