Polygyny

[Sarah]

The state or practice of having several wives at the same time;marriage to several wives. H. Spenser.

[Sarah]

Polygyny is a form of Polygamy
Polygamy is the practice of a person, of either sex, having multiple spouses, at the same time.
Polygyny is the specific instance of a man being married to multiple women...
as opposed to Polyandry which is the specific instance of a woman being married to multiple men
LDS Mormons (prior to 1890) and FLDS Mormons (currently) are known for practicing Polygyny
RLDS Mormons have never practiced polygyny, or any form of Polygamy, in the history of their religion

[Sarah]

/noun/ -- the state in which a man is married to multiple wives. Mormon ([RLDS])[PolyGamy] is exclusively of this type.