s/a/an/

actionmailer/README.rdoc

@@ -74,7 +74,7 @@ Or you can just chain the methods together like:
 
 == Receiving emails
 
-To receive emails, you need to implement a public instance method called <tt>receive</tt> that takes a
+To receive emails, you need to implement a public instance method called <tt>receive</tt> that takes an
 email object as its single parameter. The Action Mailer framework has a corresponding class method,
 which is also called <tt>receive</tt>, that accepts a raw, unprocessed email as a string, which it then turns
 into the email object and calls the receive instance method.