Duality v/s Non-duality
Duality is the inherent feature of this manifested world, while non-duality is the essence of the subtle, uncreated, eternal worlds.
Complementarity, contrast, and contradiction are all aspects of duality in this world. As examples, day and night, good and bad, right and wrong, etc., are all contrasting, contradictory and complementary. They represent the extremes of duality, and everything in between represents plurality.