diff --git a/doc/src/sgml/brin.sgml b/doc/src/sgml/brin.sgml
index 4c5eeb875f4..55b6272db62 100644
--- a/doc/src/sgml/brin.sgml
+++ b/doc/src/sgml/brin.sgml
@@ -585,7 +585,7 @@ typedef struct BrinOpcInfo
 
       <para>
        Since both key extraction of indexed values and representation of the
-       key in <acronym>GIN</acronym> are flexible, they may depend on
+       key in <acronym>BRIN</acronym> are flexible, they may depend on
        user-specified parameters.
       </para>
      </listitem>
diff --git a/doc/src/sgml/gin.sgml b/doc/src/sgml/gin.sgml
index 7a8c18a4495..07114f77199 100644
--- a/doc/src/sgml/gin.sgml
+++ b/doc/src/sgml/gin.sgml
@@ -379,7 +379,7 @@
  </para>
 
  <para>
-  Optionally, an operator class for <acronym>GIN</acronym> can supply the
+  An operator class for <acronym>GIN</acronym> can optionally supply the
   following methods:
 
   <variablelist>
@@ -406,7 +406,7 @@
      <term><function>void options(local_relopts *relopts)</function></term>
      <listitem>
       <para>
-       Defines set of user-visible parameters that control operator class
+       Defines a set of user-visible parameters that control operator class
        behavior.
       </para>
 
diff --git a/doc/src/sgml/spgist.sgml b/doc/src/sgml/spgist.sgml
index d9ecfe74ed1..5d6e893d491 100644
--- a/doc/src/sgml/spgist.sgml
+++ b/doc/src/sgml/spgist.sgml
@@ -881,7 +881,7 @@ typedef struct spgLeafConsistentOut
      <term><function>options</function></term>
      <listitem>
       <para>
-       Defines set of user-visible parameters that control operator class
+       Defines a set of user-visible parameters that control operator class
        behavior.
       </para>