A duel is a battle between two people. A duet is music for a duo, or a pair of musicians. If you have dual citizenship, you belong to two countries at once.
Most birds are dimorphic, with feathers of one color for males and another color for females.
Tell me more about Merriam-Webster's Vocabulary Builder. With her first job she discovered the dichotomy between the theories she'd been taught and the realities of professional life. In his dealings with my cranky old Aunt Louisa, Alex was always diplomatic, and she was very fond of him. A Greek diploma was an official document folded in two and sealed, or a passport. So diplomacy came to mean the international carrying and exchanging of such documents for the purpose of negotiation.