There are over 100 components in every window, but here are the top 10 most common window parts referenced when window shopping:
Head: the horizontal frame forming the top of the window.
Upper Sash: the assembly of stiles and rails made into a frame to hold the glass. (The upper sash will slide up and down in a double-hung window, but will not move in a single-hung window.)
Jamb: the main vertical frame forming the sides of the window.
Brick Mould (exterior): Outside casing around window to cover jambs and through which nails are driven to install the window.
Casing (interior): Inside casing is a flat, decorative moulding that covers the inside edge of the jambs and the rough openings between the window unit and the wall.
Muntin Bar (Grid or Grille) – any small bar that divides the window glass (panes). Muntins can either be true divided light or simulated divided light.
True divided light: A term that refers to windows in which multiple individual panes of glass or lights are assembled in the sash using muntins.
Simulated divided light: A method of constructing windows in which muntins are affixed to the inside and outside of a panel of insulating glass to simulate the look of true divided light.
Rail – the horizontal part of the sash
Lower Sash – the assembly of stiles and rails made into a frame to hold the glass.
Stile – the vertical part of the sash
Glazing – The glass panes or lights in the sash of a window. Also the act of installing lights of glass in a window sash.
Sill – the main horizontal frame forming the bottom of the window (on the outside of the window).