diff --git a/doc/api/os.markdown b/doc/api/os.markdown
index 177f4992494..7aa710585b0 100644
--- a/doc/api/os.markdown
+++ b/doc/api/os.markdown
@@ -41,7 +41,14 @@ Returns the system uptime in seconds.
 ## os.loadavg()
 
 Returns an array containing the 1, 5, and 15 minute load averages.
-This function always return `[0, 0, 0]` on Windows.
+
+The load average is a measure of system activity, calculated by the operating
+system and expressed as a fractional number.  As a rule of thumb, the load
+average should ideally be less than the number of logical CPUs in the system.
+
+The load average is a very UNIX-y concept; there is no real equivalent on
+Windows platforms.  That is why this function always returns `[0, 0, 0]` on
+Windows.
 
 ## os.totalmem()