Casement windows open by rotating horizontally to the left and right from the center, taking either the left or right edge as an axis. Some open into the interior, while others open onto the exterior. Both the left and right panels have the same dimensions: those that only open in one direction are called kannon-biraki (“goddess of mercy”), while those where one side is larger than the other are called oyako-biraki (“parent-and-child”). The ones opening in only one direction used in France since the 16th century are known as French windows.
A window that opens and closes by moving two or more parallel panels vertically over two or more grooves or rails is called a double sliding window, where both the top and bottom panels move. These sorts of windows developed primarily in the context of English stone built houses, and are commonly used even today in England as well as North America.
A window that opens and closes by moving two or more parallel panels horizontally over two or more grooves or rails is called a double sliding window, where both the left and right panels move. This sort of window is an ancient Japanese mechanism for opening and closing, and its original form can be traced back to the yarido sliding panels of the Heian era (B.C. 794 to 1185). They are commonly used even today in Japanese homes.