diff --git a/stpa handbook.md b/stpa handbook.md
index b54907670..b8598873d 100644
--- a/stpa handbook.md	
+++ b/stpa handbook.md	
@@ -36,6 +36,6 @@ Definition of [[system]]:
 
 ![[Pasted image 20210718231941.png]]
 
-The heart of STPA: 
+The heart of STPA: the control loop. 
 
 ![[Pasted image 20210718234343.png]]
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