WordNet sense 1 ((biology) a group of organisms within a species that differ in trivial ways from similar groups):

form, strain, var.

WordNet sense 2 (an event that departs from expectations):

discrepancy, variance

WordNet sense 3 (a variable quantity that is random):

variate, random variable, chance variable, stochastic variable

WordNet sense 4 (something a little different from others of the same type):

edition, variation, version

WordNet sense 5 (liable to or capable of change):

variable

WordNet sense 6 (unlike in nature or quality or form or degree):

different