polygyny        
noun [ U ] uk/pəˈlɪdʒ.ɪ.ni/ us/pəˈlɪdʒ.ɪ.ni/
 social science specialized一夫多妻(制) 
the practice of having more than one wife or permanent female sexual partner at the same time
  biology specialized(动物)一雄多雌 
the practice of a male animal having more than one female mate (= sexual partner)
 Compare: polyandry
See also: polygamy