Need to close Word documents on Mac Air..I can see no red dot, green dot or yellow dot
Word is in Full Screen mode. Simply hover your mouse at the top of the window, and the Menu bar will drop down. On the right hand side is a blue double-headed arrow. Click it, and the screen will return to a window.  (you can save the document by simply using the menu when it drops down from your mouse hover, if you wish to remain in full screen mode...oh and CMD-S is your friend (save))

Or, you can just hit ESC.