w3c
diff --git a/‎selectors4/Overview.src.html‎
Lines changed: 52 additions & 22 deletions b/‎selectors4/Overview.src.html‎
Lines changed: 52 additions & 22 deletions
@@ -413,50 +413,74 @@ <h2 id=overview>
   prepending "matches" to the contents of each cell in the "Meaning"
   column.</p>
 
-<h2 id=structure>
-Selector Syntax and Structure</h2>
+<h2 id=syntax>
+Selector Syntax</h2>
+
+<h3 id=structure>
+Structure and Terminology</h2>
 
   <p>A <dfn>selector</dfn> is a chain of one
   or more <a href="#compound">compound selectors</a>
   separated by <a href="#combinators">combinators</a>.</p>
 
   <p>A <dfn><a name=compound>compound selector</a></dfn>
-  is a chain of <a href="#simple-selectors-dfn">simple selectors</a>
+  is a chain of <a href="#simple">simple selectors</a>
   that are not separated by a <a href="#combinators">combinator</a>. It
   always begins with a <a href="#type-selectors">type selector</a> or a
-  <a href="#universal-selector">universal selector</a>. No other type
-  selector or universal selector is allowed in the sequence.</p>
+  (possibly implied) <a href="#universal-selector">universal selector</a>.
+  No other type selector or universal selector is allowed in the sequence.</p>
 
   <p>A <dfn><a name=simple-selectors-dfn></a><a
-  href="#simple-selectors">simple selector</a></dfn> is either a <a
+  href="#simple">simple selector</a></dfn> is either a <a
   href="#type-selectors">type selector</a>, <a
   href="#universal-selector">universal selector</a>, <a
   href="#attribute-selectors">attribute selector</a>, <a
   href="#class-html">class selector</a>, <a
   href="#id-selectors">ID selector</a>, or <a
   href="#pseudo-classes">pseudo-class</a>.</p>
 
-  <p><dfn>Combinators</dfn> are: whitespace, &quot;greater-than
+  <p><dfn>Combinators</dfn> are punctuation that represent a particular
+  kind of relationship between the compound selectors on either side.
+  Combinators in Selectors level 4 include: whitespace, &quot;greater-than
   sign&quot; (U+003E, <code>&gt;</code>), &quot;plus sign&quot; (U+002B,
-  <code>+</code>) and &quot;tilde&quot; (U+007E, <code>~</code>).  White
-  space may appear between a combinator and the simple selectors around
-  it. <a name=whitespace></a>Only the characters "space" (U+0020), "tab"
-  (U+0009), "line feed" (U+000A), "carriage return" (U+000D), and "form
-  feed" (U+000C) can occur in whitespace. Other space-like characters,
-  such as "em-space" (U+2003) and "ideographic space" (U+3000), are
-  never part of whitespace.</p>
-
-  <p>The elements of a document tree that are represented by a selector
-  are the <dfn><a name=subject></a>subjects of the selector</dfn>. A
-  selector consisting of a single compound selector
-  represents any element satisfying its requirements. Prepending another
-  compound selector and a combinator to a sequence imposes
-  additional matching constraints, so the subjects of a selector are
-  always a subset of the elements represented by the last compound selector.</p>
+  <code>+</code>) and &quot;tilde&quot; (U+007E, <code>~</code>).
+  <a href="#whitespace">White space</a> may appear between a combinator
+  and the simple selectors around it.</p>
 
   <p>An empty selector, containing no compound selector, is an
   <a href="#invalid">invalid selector</a>.</p>
 
+<h3 id=subject>
+Subject of a Selector
+
+  <p>The elements of a document tree that are represented by a selector
+  are the <dfn>subjects</dfn> of the selector.
+
+  <p>By default, the subjects of a selector are the elements represented
+  by the last compound selector in the selector. Thus a selector consisting
+  of a single compound selector represents any element satisfying its
+  requirements. Prepending another compound selector and a combinator
+  to a sequence imposes additional matching constraints, so the subjects of
+  the selector are always a subset of the elements represented by the last
+  compound selector.</p>
+
+  <p>The subject of the selector can be explicitly identified by prepending
+  an exclamation mark (!) to one of the compound selectors in a selector.
+  Although the element structure that the selector represents is the same
+  with or without the exclamation mark, indicating the subject in this way
+  can change which compound selector represents the subject in that structure.
+
+  <div class="example">
+  <p>For example, the following selector represents a list item <code>LI</code>
+    unique child of an ordered list <code>OL</code>:
+    <pre>OL &gt; LI:only-child</pre>
+    <p>However the following one represents an ordered list <code>OL</code>
+    having a unique child, that child being a <code>LI</code>:
+    <pre>!OL &gt; LI:only-child</pre>
+    <p>The structures represented by these two selectors are the same, but the
+    subjects of the selectors are not.
+  </div>
+
 <h3 id=case-sensitive>
 Characters and case sensitivity</h3>
 
@@ -469,6 +493,12 @@ <h3 id=case-sensitive>
   case-sensitive. Case sensitivity of namespace prefixes is defined in
   [[!CSS3NAMESPACE]].</p>
 
+  <p><dfn id=whitespace>White space</dfn> in Selectors consists of the
+  characters SPACE (U+0020), TAB (U+0009), LINE FEED (U+000A),
+  CARRIAGE RETURN (U+000D), and FORM FEED (U+000C) can occur in whitespace.
+  Other space-like characters, such as EM SPACE (U+2003) and
+  IDEOGRAPHIC SPACE (U+3000), are never part of white space.
+
   <p>Characters in Selectors can be escaped with a backslash according
   to the same <a href="http://www.w3.org/TR/CSS21/syndata.html#characters">escaping
   rules</a> as CSS. [[!CSS21]].</p>