diff --git a/Changes b/Changes
index cf6c712..262f721 100755
--- a/Changes
+++ b/Changes
@@ -1,8 +1,9 @@
-0.51 2023-06-09
+0.51 2023-07-21
         - Support defined log file in configuration. (diewald)
         - Remove experimental_client_registration setting
           and make client registration mandatory in OAuth
           (diewald)
+        - Introduce 'reserved terms' in documentation (diewald)
 
 0.50 2023-05-08
         - Improvement of NKJP-annotation helper. (diewald)
diff --git a/templates/de/doc/ql/poliqarp-plus.html.ep b/templates/de/doc/ql/poliqarp-plus.html.ep
index d203a98..ed4a225 100644
--- a/templates/de/doc/ql/poliqarp-plus.html.ep
+++ b/templates/de/doc/ql/poliqarp-plus.html.ep
@@ -51,6 +51,29 @@
 
   %= doc_query poliqarp => loc('Q_poliqarp_rexi', '** "r(u|a)n"/xi'), cutoff => 1
 
+  <h4 id="reserved">Geschützte Begriffe</h4>
+
+  <p>Die folgenden Wörter sind Teil der Anfragesprache von Poliqarp+ und können daher nicht in der Kurzschreibung für einfache Segmente verwendet werden. Um dennoch nach ihnen suchen zu können, ist die Schreibung als <%= embedded_link_to 'doc', 'komplexe Segmente', 'ql', 'poliqarp-plus#complex'%> nötig (z.B. <code>[orth='contains']</code>):
+  
+  <ul>
+    <li><code>contains</code></li>
+    <li><code>dependency</code></li>
+    <li><code>dominates</code></li>
+    <li><code>endswith</code></li>
+    <li><code>endsWith</code></li>
+    <li><code>focus</code></li>
+    <li><code>i</code> und <code>I</code></li>
+    <li><code>meta</code></li>
+    <li><code>matches</code></li>
+    <li><code>overlaps</code></li>
+    <li><code>relatesTo</code></li>
+    <li><code>split</code></li>
+    <li><code>startswith</code> und <code>startsWith</code></li>
+    <li><code>submatch</code></li>
+    <li><code>within</code></li>
+    <li><code>x</code> und <code>X</code></li>
+  </ul>
+
 </section>
 
 <section id="complex">
diff --git a/templates/doc/ql/poliqarp-plus.html.ep b/templates/doc/ql/poliqarp-plus.html.ep
index e97fbdd..2b66d8d 100644
--- a/templates/doc/ql/poliqarp-plus.html.ep
+++ b/templates/doc/ql/poliqarp-plus.html.ep
@@ -50,6 +50,31 @@
   <p>You can again apply the <code>/i</code> flag to regular expressions to search case insensitive.</p>
 
   %= doc_query poliqarp => loc('Q_poliqarp_rexi', '** "r(u|a)n"/xi'), cutoff => 1
+
+  <h4 id="reserved">Reserved terms</h4>
+
+  <p>The following terms are <em>reserved words</em> in Poliqarp+ and can therefore not be used in short notation of simple segments.
+    Use the notation for <%= embedded_link_to 'doc', 'complex segments', 'ql', 'poliqarp-plus#complex'%> to query them (e.g. <code>[orth='contains']</code>):</p>
+
+  <ul>
+    <li><code>contains</code></li>
+    <li><code>dependency</code></li>
+    <li><code>dominates</code></li>
+    <li><code>endswith</code></li>
+    <li><code>endsWith</code></li>
+    <li><code>focus</code></li>
+    <li><code>i</code> and <code>I</code></li>
+    <li><code>meta</code></li>
+    <li><code>matches</code></li>
+    <li><code>overlaps</code></li>
+    <li><code>relatesTo</code></li>
+    <li><code>split</code></li>
+    <li><code>startswith</code> and <code>startsWith</code></li>
+    <li><code>submatch</code></li>
+    <li><code>within</code></li>
+    <li><code>x</code> and <code>X</code></li>
+  </ul>
+
 </section>
 
 <section id="complex">