Sorry, I have read the misspelling 'coersion' one time too many.

doc/src/sgml/history.sgml

@@ -227,7 +227,7 @@
    <listitem>
     <para>
      Additional <acronym>SQL92</acronym>-compliant language features have been added,
-     including primary keys, quoted identifiers, literal string type coersion, 
+     including primary keys, quoted identifiers, literal string type coercion,
      type casting, and binary and hexadecimal integer input.
     </para>
    </listitem>

doc/src/sgml/release.sgml

@@ -414,7 +414,7 @@ Fix bug in pg_dump -z
 Memory overrun cleanups(Tatsuo)
 Fix for lo_import crash(Tatsuo)
 Adjust handling of data type names to suppress double quotes(Thomas)
-Use type coersion for matching columns and DEFAULT(Thomas)
+Use type coercion for matching columns and DEFAULT(Thomas)
 Fix deadlock so it only checks once after one second of sleep(Bruce)
 Fixes for aggregates and PL/pgsql(Hiroshi)
 Fix for subquery crash(Vadim)
@@ -475,7 +475,7 @@ EXPLAIN all indices used(Tom)
 Implement CASE, COALESCE, NULLIF  expression(Thomas)
 New pg_dump table output format(Constantin)
 Add string min()/max() functions(Thomas)
-Extend new type coersion techniques to aggregates(Thomas)
+Extend new type coercion techniques to aggregates(Thomas)
 New moddatetime contrib(Terry)
 Update to pgaccess 0.96(Constantin)
 Add routines for single-byte "char" type(Thomas)
@@ -672,7 +672,7 @@ Fix for lo_import() crash(Bruce)
 Better search for install program(Tom)
 Timezone fixes(Tom)
 HPUX fixes(Tom)
-Use implicit type coersion for matching DEFAULT values(Thomas)
+Use implicit type coercion for matching DEFAULT values(Thomas)
 Add routines to help with single-byte (internal) character type(Thomas)
 Compilation of libpq for Win32 fixes(Magnus)
 Upgrade to PyGreSQL 2.2(D'Arcy)
@@ -734,7 +734,7 @@ asynchronous messages and interrupts thanks to Tom Lane.
 
 <listitem>
 <para>
-The parser will now perform automatic type coersion to match arguments
+The parser will now perform automatic type coercion to match arguments
 to available operators and functions, and to match columns and expressions
 with target columns. This uses a generic mechanism which supports
 the type extensibility features of <productname>Postgres</productname>.

doc/src/sgml/typeconv.sgml

@@ -14,7 +14,7 @@ to understand the details of the type conversion mechanism.
 However, the implicit conversions done by <productname>Postgres</productname>
 can affect the apparent results of a query, and these results
 can be tailored by a user or programmer
-using <emphasis>explicit</emphasis> type coersion.
+using <emphasis>explicit</emphasis> type coercion.
 </para>
 
 <para>
@@ -26,7 +26,7 @@ for more information on specific data types and allowed functions and operators.
 
 <para>
 The Programmer's Guide has more details on the exact algorithms used for
-implicit type conversion and coersion.
+implicit type conversion and coercion.
 </para>
 
 <sect1>
@@ -163,14 +163,14 @@ All type conversion rules are designed with several principles in mind:
 <itemizedlist mark="bullet" spacing="compact">
 <listitem>
 <para>
-Implicit conversions should never have suprising or unpredictable outcomes.
+Implicit conversions should never have surprising or unpredictable outcomes.
 </para>
 </listitem>
 
 <listitem>
 <para>
-User-defined types, of which the parser has no apriori knowledge, should be
-"higher" in the type heirarchy. In mixed-type expressions, native types shall always
+User-defined types, of which the parser has no a-priori knowledge, should be
+"higher" in the type hierarchy. In mixed-type expressions, native types shall always
 be converted to a user-defined type (of course, only if conversion is necessary).
 </para>
 </listitem>