Alternatively called a cascading menu, a submenu is a menu contained within another menu. For example, a submenu is often identified by having a small arrow or chevron pointing to the right at the edge of the option. Users using the keyboard to navigate a menu can access a submenu by pressing the right arrow key or collapse the submenu by pressing the left arrow key.
In the picture, the “Recent Files” menu option has a submenu arrow. If Recent Files was selected, it shows a cascading menu of all recent files opened in this program.
Menu, Operating system terms
