WindowFloating is a notebook option that specifies whether the window for the notebook should float on top of other windows when it is displayed on the screen.
WindowMovable is a notebook option that specifies whether to allow the window for the notebook to be moved around interactively on the screen.
WindowOpacity is a notebook option that determines the overall opacity of a displayed window.
WindowStatusArea is a notebook option that specifies what should appear in the status area in the frame of the window used to display the notebook.
WindowToolbars is a notebook option that specifies the toolbars to include at the top of the window used to display the notebook on the screen.
WordBoundary represents a boundary between words for purposes of matching in StringExpression.
Word
(Built-in Mathematica Symbol) Word represents a word in Read, Find, and related functions.
WordSearch is an option for Find and FindList that specifies whether the text searched for must appear as a word.
WriteString[channel, expr_1, expr_2, ...] converts the expr_i to strings, and then writes them in sequence to the specified output channel.
XMLObject["type"] represents the head of an XML object in symbolic XML.