**Defined in theory: Kif-sets****Source code: kif-sets.lisp**

**Documentation:**The sentence {tt (subset $tau_1$ $tau_2$)} is true if and only if $tau_1$ and $tau_2$ are sets and the objects in the set denoted by $tau_1$ are contained in the set denoted by $tau_2$.

**Arity:**2**Domain:**Set**Range:**Set

(<=> (Subset ?S1 ?S2) (And (Set ?S1) (Set ?S2) (Forall (?X) (=> (Member ?X ?S1) (Member ?X ?S2)))))

**Source:**KIF Version 3.0 Specification