diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 970d8d99e0c..0c5f8068c7b 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -666,14 +666,16 @@
 
       <row>
        <entry> <literal>!</literal> </entry>
-       <entry>factorial</entry>
+       <entry>factorial
+        (deprecated, use <function>factorial()</function> instead)</entry>
        <entry><literal>5 !</literal></entry>
        <entry><literal>120</literal></entry>
       </row>
 
       <row>
        <entry> <literal>!!</literal> </entry>
-       <entry>factorial (prefix operator)</entry>
+       <entry>factorial as a prefix operator
+        (deprecated, use <function>factorial()</function> instead)</entry>
        <entry><literal>!! 5</literal></entry>
        <entry><literal>120</literal></entry>
       </row>
@@ -856,6 +858,19 @@
        <entry><literal>2.71828182845905</literal></entry>
       </row>
 
+      <row>
+       <entry>
+        <indexterm>
+         <primary>factorial</primary>
+        </indexterm>
+        <literal><function>factorial(<type>bigint</type>)</function></literal>
+       </entry>
+       <entry><type>numeric</type></entry>
+       <entry>factorial</entry>
+       <entry><literal>factorial(5)</literal></entry>
+       <entry><literal>120</literal></entry>
+      </row>
+
       <row>
        <entry>
         <indexterm>
diff --git a/doc/src/sgml/ref/create_operator.sgml b/doc/src/sgml/ref/create_operator.sgml
index 818e3a2315a..73ccac7fecf 100644
--- a/doc/src/sgml/ref/create_operator.sgml
+++ b/doc/src/sgml/ref/create_operator.sgml
@@ -87,11 +87,18 @@ CREATE OPERATOR <replaceable>name</replaceable> (
 
   <para>
    At least one of <literal>LEFTARG</> and <literal>RIGHTARG</> must be defined.  For
-   binary operators, both must be defined. For right  unary
+   binary operators, both must be defined. For right unary
    operators, only <literal>LEFTARG</> should be defined, while for left
    unary operators only <literal>RIGHTARG</> should be defined.
   </para>
 
+  <note>
+   <para>
+    Right unary, also called postfix, operators are deprecated and will be
+    removed in <productname>PostgreSQL</productname> version 14.
+   </para>
+  </note>
+
   <para>
    The <replaceable class="parameter">function_name</replaceable>
    procedure must have been previously defined using <command>CREATE