Polygamy

Polygamy is the practice of having marriages involving more than two people.

It is illegal in the United States, though estimates of the number of Americans who live in polygamy vary from 30,000 to 100,000. It is legal in some African and Middle Eastern Countries.

Types
The most commonly practiced form of polygamy is polygyny, which is where a man has multiple wives at once. Polyandry is where a woman has more than one husband.