Tenon: a rectangular projection cut out of a piece of wood for insertion into a mortise.
Tempered glass. Treated glass that is strengthened by reheating it to just below the melting point and then suddenly cooling it. When it breaks, it shatters into small pieces to reduce hazard.
Tilt latch:The mechanism that unlocks the sash and allows it to tilt in from the main frame.
Tilt Window: A window that the sashes tilt inward for easy cleaning of the outside glass surface.
Tilt & turn: A window that opens inwards being fixed at the side and tilt at the top inside.
Thermal break.A material of low conductance placed between two elements of higher conductance to reduce the flow of heat. Often used in aluminum windows.
Transom: A small window above a door or another window. A transom joint the horizontal member separating a door from a window panel above the door, or separating one window above another.
Triple glazing:A sash glazed with three lights of glass, enclosing two separate air spaces.