Final answer:
The most common form of marriage practiced in the United States is monogamy, where one person is married to only one person at a time. However, marriage customs can vary across different cultures and societies. There is ongoing debate in the United States about what constitutes a marriage.
Step-by-step explanation:
In American and European cultures, the most common form of marriage is a union of two people. This form of marriage is called monogamy, where one person is married to only one person at a time. However, marriage customs can vary across different cultures and societies. For example, in some small-scale farming cultures, a man may have multiple wives due to the need for children to help with agricultural work. Additionally, there is ongoing debate in the United States about what constitutes a marriage, with some people advocating for same-sex marriage and others arguing for traditional heterosexual marriages.