[css-display-3] Bind typically to single rather than principal. #3157

Author: fantasai

css-display-3/Overview.bs

@@ -73,7 +73,8 @@ Introduction</h2>
 	Then, for each [=CSS/element=],
 	CSS generates zero or more <a>boxes</a>
 	as specified by that element's 'display' property.
-	Typically, an element generates a single <a>principal box</a>,
+	Typically, an element generates a single <a>box</a>,
+	the <a>principal box</a>,
 	which represents itself and contains its contents in the <a>box tree</a>.
 	However, some 'display' values
 	(e.g. ''display: list-item'')