frontier for m-polar neutrosophic sets (MPNSs) with illustrative examples. We discuss some results which holds for classical set theory but do not hold for m-polar neutrosophic set theory. We introduce cosine similarity measure and set theoretic similarity measures for MPNSs. Furthermore, we present two algorithms for multi-criteria decision-making (MCDM) in medical diagnosis by using m-polar neutrosophic set (MPNS) and m-polar neutrosophic topology.