operating system (Or "drop-down menu", "pop-down menu") A

menu in a graphical user interface, whose title is

normally visible but whose contents are revealed only when the

user activates it, normally by pressing the mouse button

while the pointer is over the title, whereupon the menu

items appear below the title. The user may then select an

item from the menu or click elsewhere, in either case the menu

contents are hidden again. A menu item is selected either by

dragging the mouse from the menu title to the item and

releasing or by clicking the title and then the item.