fix typo

Author: cgilliard

bip-XXXX.mediawiki

@@ -15,7 +15,7 @@
 
 This document describes a signature format for signing messages with Bitcoin private keys.
 
-The specification is intended to describe the standard for signatures of messages that can be signed and verfied between different clients that exist in the field today. Note: that a new signature format has been definied which has a number of advantages over this BIP, but to be backwards compatible with existing implementations this BIP will be useful. See BIP 322 [1] for full details on the new signature scheme.
+The specification is intended to describe the standard for signatures of messages that can be signed and verfied between different clients that exist in the field today. Note: that a new signature format has been defined which has a number of advantages over this BIP, but to be backwards compatible with existing implementations this BIP will be useful. See BIP 322 [1] for full details on the new signature scheme.
 
 One of the key problems in this area is that there are several different types of Bitcoin addresses and without introducing specific standards it is unclear which type of address format is being used. See [2]. This BIP will attempt to address these issues and define a clear and concise format for Bitcoin signatures.