diff --git a/doc/site/modules/core/num.markdown b/doc/site/modules/core/num.markdown
index 6070396f..968a5753 100644
--- a/doc/site/modules/core/num.markdown
+++ b/doc/site/modules/core/num.markdown
@@ -112,6 +112,10 @@ System.print((-3.2).round) //> -3
 System.print((-3.7).round) //> -4
 </pre>
 
+### **sign**
+
+The sign of the number, expressed as a -1, 1 or 0, for negative and positive numbers, and zero.
+
 ### **sin**
 
 The sine of the number.