Heterogeneity is a word that signifies diversity. A classroom consisting of people from lots of different backgrounds would be considered having the quality of heterogeneity.
The prefix hetero- means "other or different," while the prefix homo- means "the same." Heterogeneity is often used in contrast to homogeneity, which is when two or more people or things are alike. Heterogeneity can also refer to something that is made up of lots of different elements, like a local dialect composed of various languages.