WordNet sense 1 (an event that departs from expectations):

discrepancy, variant

WordNet sense 2 (discord that splits a group):

division

WordNet sense 3 (a difference between conflicting facts or claims or opinions):

disagreement, divergence

WordNet sense 4 (the quality of being subject to variation):

variability, variableness

WordNet sense 5 (an activity that varies from a norm or standard):

variation