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1640s, from Medieval Latin heterogeneitas, from heterogeneus, from Greek heterogenes (see heterogeneous).
heterogeneity het·er·o·ge·ne·i·ty (hět'ə-rō'jə-nē'ĭ-tē)n. The quality or state of being heterogeneous.
Cultural, social, biological, or other differences within a group. (Compare homogeneity.)