A manufactured assembly of a frame, sash, glazing and necessary hardware, made to fit an opening in a wall. Components of a window may include the following:

• Window sill: horizontal member at the base of a window opening.
• Window head: horizontal member at the top of a window opening.
• Window jamb: either of the vertical members at the sides of a window opening.
• Mullion: A vertical member between the glazed units.
• Rail: A horizontal member between the glazed units.
• Glazing: The glass portion of the window.
• IGU: Insulated glazing unit. Double or triple panes of glass sealed together to provide insulation value.  The still gas between the panes acts as the insulation.
• Condensation track: a channel at the interior sill level of the window intended to intercept small amounts of water condensing on the interior surface of the glass.