diff --git a/theories/properties.v b/theories/properties.v
index bcd72d6..c277856 100644
--- a/theories/properties.v
+++ b/theories/properties.v
@@ -96,4 +96,11 @@ Module Typing.
     - hauto lq:on ctrs:Wt use:ren_up.
   Qed.
 
+  (* Liftable: stable *)
+(* If a well-typed term is liftable, then it should remain well-typed at the same level
+if the floating variables are lifted  *)
+
+  (* Upgrade *)
+  (* If Γ ⊢ a ;; ℓ ∈ A, we want to lift up the levels in Γ  *)
+
 End Typing.