[css-values-4] Editorial tweaks to <<ratio>>.

Author: fantasai

css-values-4/Overview.bs

@@ -1239,7 +1239,9 @@ Combination of Percentage and Dimension Mixes</h4>
 Ratios: the <<ratio>> type</h3>
 
 	Ratio values are denoted by <dfn id=ratio-value>&lt;ratio></dfn>,
-	and indicate a value that is a ratio of two numeric values.
+	and represent the ratio of two numeric values.
+	It most often represents an aspect ratio,
+	relating a width (first) to a height (second).
 
 	When written literally,
 	a <dfn export>ratio</dfn> has the syntax:
@@ -1251,10 +1253,6 @@ Ratios: the <<ratio>> type</h3>
 	If only one <<number>> is provided,
 	the second defaults to ''1''.
 
-	Uses of <<ratio>> must specify what the two values are;
-	generally, however,
-	it is expected that they will be a ratio of a width (first) and a height (second).
-
 	The computed value of a <<ratio>> is the pair of numbers provided,
 	unless both numbers are zero,
 	in which case the computed value is the pair (1, 0) (same as ''1 / 0'').
@@ -1271,7 +1269,7 @@ Ratios: the <<ratio>> type</h3>
 	and compare the results.
 	For example, <css>3/2</css> is less than <css>2/1</css>,
 	because it resolves to 1.5 while the second resolves to 2.
-	(In other words, "tall" ratios are less than "wide" ratios.)
+	(In other words, “tall” aspect ratios are less than “wide” aspect ratios.)
 
 <h4 id='combine-ratio'>
 Combination of <<ratio>></h4>