diff --git a/preface.asciidoc b/preface.asciidoc
index 1666c07b..324fdc22 100644
--- a/preface.asciidoc
+++ b/preface.asciidoc
@@ -117,6 +117,10 @@ address (aka public key)::
 ((("public key", see="bitcoin address")))
 	A bitcoin address looks like +1DSrfJdB2AnWaFNgSbv3MZC2m74996JafV+, they always start with a one. Just like you ask others to send an email to your email address, you would ask others to send you bitcoin to your bitcoin address.
 
+bip::
+((("bip"))) 
+    Bitcoin Improvement Proposals.  A set of proposals that members of the bitcoin community have submitted to improve bitcoin.  For example BIP0021 is a proposal to improve the bitcoin URI scheme.
+
 bitcoin::
 ((("bitcoin"))) 
     The name of the currency unit (the coin), the network and the software