The width, in pixels, of the font's space character.
@item average-width
-The average width of the font characters. If this is zero, Emacs uses
-the value of @var{space-width} instead, when it calculates text layout
-on display.
+The average width of the font characters. Emacs uses this for
+calculating text layout on display; if the value of @var{average-width}
+is zero, Emacs uses the value of @var{space-width} instead for those
+purposes.
@item filename
The file name of the font as a string. This can be @code{nil} if the