Add a non-normative explanation of "proper name" to 3.1.2 Language of Parts understanding

understanding/20/language-of-parts.html

@@ -50,6 +50,14 @@ <h2>Intent of Language of Parts</h2>
          <p>As these problems are caused by limitations of user agents and assistive technologies, and are outside of an author's control, they <em>don't fail</em> the requirements of this success criterion. When evaluating content against this success criterion, auditors can therefore not solely rely on the spoken output from assistive technologies, but must verify whether or not changes in natural language have been identified correctly in the underlying code or markup.</p>
       </div>
 
+      <p>While the concept and definition of <em>proper names</em> varies across languages,
+      it generally refers to a name which is taken to distinctly identify its referent – including,
+      but not limited to, a product's brand name or the name of a specific person or place. Proper names can be used
+      across languages without translation (though it may be transliterated from its original writing system). Proper names
+      generally don't require an explicit programmatic change of language. As a simple example, in an English
+      document about philosophy, the name "Albert Camus" does <em>not</em> need to be explicitly denoted
+      as being in French.</p>
+
       <p>Individual words or phrases in one language can become part of another language. For
          example, "rendezvous" is a French word that has been adopted in English, appears in
          English dictionaries, and is properly pronounced by English screen readers. Hence
@@ -64,6 +72,34 @@ <h2>Intent of Language of Parts</h2>
          text.
       </p>
 
+      <div class="note">
+         <p>
+            Pronunciation quality and accuracy can vary significantly across
+            screen readers and speech synthesizers.
+         </p>
+         <p>
+            Although a borrowed French word like “rendezvous” may be pronounced
+            intelligibly in an English context, others may not. This can be
+            especially true of <a
+            href="#:~:text=While%20the%20concept,being%20in%20French.">proper
+            names</a>.
+         </p>
+         <p>
+            Though <strong>not normatively required</strong> to satisfy this
+            success criterion, it’s a best practice to programmatically indicate
+            the source language of these words to encourage accurate
+            pronunciation and improve understandability. For example, using the
+            <code>lang</code> attribute in HTML:
+         </p>
+         <pre><code class="language-html">It can be a &lt;span lang="fr"&gt;faux pas&lt;/span&gt; to omit the &lt;code&gt;lang&lt;/code&gt; attribute.</code></pre>
+         <p>
+            When the language of the part uses a different writing system (or a transliteration)
+            than the language of the page, explicitly specifying the source language is
+            especially helpful for accurate pronunciation:
+         </p>
+         <pre><code class="language-html">Good &lt;span lang="zh-Latn-pinyin"&gt;feng shui&lt;/span&gt; begins with good markup.</code></pre>
+      </div>
+
       <p>Most professions require frequent use of technical terms which may originate from
          a foreign language. Such terms are usually not translated to all languages. The universal
          nature of technical terms also facilitate communication between professionals.