Lowercase unnecessary capitalization of "Undefined".

index.html

@@ -5730,7 +5730,7 @@ <h3>Providing Default Language and Direction</h3>
 data-cite="JSON-LD#string-internationalization">String Internationalization</a>
 section of the [[JSON-LD]] specification for more information. Natural language
 string values that do not have a language associated with them SHOULD be
-treated as if the language value is `Undefined` (language tag "`und`"). Natural
+treated as if the language value is `undefined` (language tag "`und`"). Natural
 language string values that do not have a base direction associated with them
 SHOULD be treated as if the direction value is "`auto`".
         </p>