"The man said, “This is now bone of my bones and flesh of my flesh; she shall be called ‘woman,’ for she was taken out of man. That is why a man leaves his father and mother and is united to his wife, and they become one flesh." - Genesis 2:23-24
Monogamy is the most common form of marriage in civilized Christian countries. In a normal sense it is marriage between a man and a woman.
The term polygamy (many marriages in late Greek) is used in related ways in social anthropology and sociobiology and sociology. Polygamy can be most succinctly defined as any "form of marriage in which a person has more than one spouse."
In social anthropology, polygamy is the practice of marriage to more than one spouse simultaneously. Historically, polygamy has been practiced as polygyny (one man having more than one wife), or as polyandry (one woman having more than one husband), or, less commonly as "polygamy" (having many wives and many husbands at one time). (See "Forms of Polygamy" below.) In contrast monogamy is the practice each person having only one spouse at a time. Like monogamy, the term is often used in a de facto sense, applying regardless of whether the relationships are recognized by the state (see marriage for a discussion on the extent to which states can and do recognize potentially and actually polygamous forms as valid).