Monogamy
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
The marriage of one wife only or the state of such as are restrained to a single wife.
Webster.
A marriage contracted between one man and one woman, in exclusion of all the rest of mankind. The term is used in opposition to "bigamy" and "polygamy."
Wolff, Dr. de la Nat. § 857.