+definition lexs_frees_confluent: relation (relation3 lenv term term) ≝
+ λRN,RP.
+ ∀f1,L1,T. L1 ⊢ 𝐅*⦃T⦄ ≡ f1 →
+ ∀L2. L1 ⦻*[RN, RP, f1] L2 →
+ ∃∃f2. L2 ⊢ 𝐅*⦃T⦄ ≡ f2 & f2 ⊆ f1.
+
+definition R_confluent2_lfxs: relation4 (relation3 lenv term term)
+ (relation3 lenv term term) … ≝
+ λR1,R2,RP1,RP2.
+ ∀L0,T0,T1. R1 L0 T0 T1 → ∀T2. R2 L0 T0 T2 →
+ ∀L1. L0 ⦻*[RP1, T0] L1 → ∀L2. L0 ⦻*[RP2, T0] L2 →
+ ∃∃T. R2 L1 T1 T & R1 L2 T2 T.
+
+(* Basic properties *********************************************************)