WordNet sense 1 (a league ranked by quality):

class

WordNet sense 2 (a unit of the United States Air Force usually comprising two or more wings):

air division

WordNet sense 3 (a group of ships of similar type):

naval division

WordNet sense 4 (discord that splits a group):

variance

WordNet sense 5 (one of the portions into which something is regarded as divided and which together constitute a whole):

part, section

WordNet sense 6 (the act of dividing or partitioning; separation by the creation of a boundary that divides or keeps apart):

partition, segmentation, partitioning, sectionalisation, sectionalization