The number of sets of chromosomes within a cell or organism. Each set is designated "n" so one set is n is haploid, two sets is 2n is diploid, three sets is 3n is triploid, four sets is 4n is tetraploid, etc. Also, unspecified multiple sets (but more than two) is polyploidy, and extremely large number of sets may be designated by number (for example 15-ploid for fifteen sets).