if there is a "set" w in v that is a standard model of zf, and the ordinal κ is the set of ordinals that occur in w, then l is the l of w. if there is a set that is a standard model of zf, then the smallest such set is such a l. this set is called the minimal model of zfc. using the downward löwenheim–skolem theorem, one can show that the minimal model (if it exists) is a countable set.