Today, there are many ways to describe relationships. The queer community has embraced many nuances to sexuality, and more broadly, society has been more ready to have conversations about monogamy. So what's the difference between polyamory and polygamy—two different relationship types with very similar names?
Polygamy is the term for having multiple spouses and is practiced in cultures worldwide. In the United States, TV shows such as Big Love and Sister Wives have portrayed the practice in Fundamentalist Mormonism. Fundamentalist Mormonism is a sect or religion that follows the early Mormon teachings which allowed for polygamy. Modern Mormonism, or The Church of Jesus Christ of Latter-day Saints, differs from these fundamentalist groups because they no longer allow the practice of polygamy. In fact, the mainstream LDS church tries to distance itself from the fundamentalists because of the negative stigma of polygamy.
Polygamist groups that get the most publicity in the media and on TV shows are heterosexual, religious-based, patriarchal, perceived and represented as cults, and sometimes involve teen girls who are married to an older man who has more than one wife. Generally, these women are not free to have sexual relationships with others, but consider themselves family with the other wives of their husband. Polygamy is also sometimes called "plural marriage." Women are often subservient and have little or no rights.
However, those represented in the news and on TV are not the only kinds of polygamists, and many polygamists disapprove of marrying young girls to older men. It is common for people living in polygamist relationships to do so in secret because of fears relating to being involved in a practice that is seen as deviant. One of the most notorious groups of polygamists is the Fundamentalist Church of Jesus Christ of Latter-day Saints (or FLDS), whose leader Warren Jeffs is in prison for sexually assaulting young girls.
Polygamy is illegal in the United States, although in many countries and religions having more than one spouse is not illegal.
Polyamory is usually not related to a religion and is unrelated to marriage, although some polyamorous people are married or have participated in commitment ceremonies with their partners. Polyamory means having multiple loving relationships, usually, but they're not necessarily sexual. People in polyamorous relationships stress the importance of open communication and equal relationships between partners whether male or female. Usually all parties involved know about the other partners and choose to be in those relationships. While polygamists are typically heterosexual, many sexualities can come together in a polyamorous relationship.
Sometimes people in these relationships are called "swingers" or "open," although swinger most often refers to married couples who have consensual sexual relationships outside of their marriage. People who are poly often stress the loving relationship over the sex. In fact, it is their ability to have multiple loving relationships with more than one partner which defines them. And in many cases, people who are polyamorous stress the importance of being ethical and caring about the feelings of everyone involved. Often people who are poly only date other poly people.
People have open relationships for a variety of reasons. In the feminist community of the '70s, monogamy and marriage were sometimes seen as patriarchal constructs and being open to relationships with more than one person was viewed as counter-culture, radical, and feminist. Some people find that one person can't meet all of their needs and they choose to be involved with multiple partners. Polyamory can also describe a relationship where more than two people are in a relationship together.