چكيده فارسي :
One of the problems in fuzzy group theory is concerned with classifying the fuzzy normal subgroups of a finite group. In this paper, we have treated classifying the fuzzy normal subgroups of all finite groups of order 16 and 20, by using the natural equivalence relation. In this case, the corresponding equivalence classes of fuzzy normal subgroups of a group G are closely connected to the chains of normal subgroups in G. In fact, for determining the number of these classes, we have calculated the number of all chains of normal subgroups of G that terminate in G.
