duality

noun (plural dualities)

• 1 [mass noun] the quality or condition of being dual:this duality of purpose was discernible in the appointments
• Mathematics the property of two theorems, expressions, etc., of being dual to each other.
• Physics the quantum-mechanical property of being regardable as both a wave and a particle.

• 2an instance of opposition or contrast between two concepts or two aspects of something; a dualism:his photographs capitalize on the dualities of light and dark, stillness and movement