diff --git a/src/fiber_package/membership_tag.py b/src/fiber_package/membership_tag.py
index 04ba057..63abc24 100644
--- a/src/fiber_package/membership_tag.py
+++ b/src/fiber_package/membership_tag.py
@@ -8,6 +8,7 @@ class Membership(StrEnum):
     member = "member"
     activity_goer = "activity_goer"
     alumn = "alumn"
+    extern = "extern" # extern is linked to association A if they ever visisted an activity of association A
 
 
 def validate_visibility_tag(v: str) -> str: