diff --git a/README.md b/README.md
index d022ed5..5bd8bd9 100644
--- a/README.md
+++ b/README.md
@@ -3,11 +3,11 @@
 Go by Example book source.
 
 
-### Reordering
+### Numbering
 
 ```console
 $ mate tool/index.txt
-$ tool/renumber
+$ tool/number
 ```
 
 
@@ -16,4 +16,3 @@ $ tool/renumber
 ```console
 $ tool/gofmt
 ```
-
diff --git a/tool/renumber b/tool/number
similarity index 100%
rename from tool/renumber
rename to tool/number
diff --git a/tool/renumber.go b/tool/number.go
similarity index 97%
rename from tool/renumber.go
rename to tool/number.go
index c8984d3..e6c66a4 100644
--- a/tool/renumber.go
+++ b/tool/number.go
@@ -1,4 +1,4 @@
-// Renumber the .go content files according to the
+// (Re-)number the .go content files according to the
 // order in index.txt.
 
 package main