Trapezoid windows are four sided and either come as a left or a right trapezoid when they are viewed from the exterior. You can determine this by which side the short leg of the trapezoid is on. If the short leg is on the right, then it is a right trapezoid, just as it would be if the short leg is on the left, then that would be a left trapezoid.
These units are available in choice of glass, removal of J-Channel, Extension Jambs and the ability to mull to another unit. There grid options are either Profile or Flat (90º Intersects Only), and need a drawing.
In order to appropriately order a trapezoid window, you must have the Width of Base (X), Height of Long Leg (Y) and Height of the Short Leg, which must be a minimum of 6 inches (Z).