In polygamy, one person has multiple partners, whereas, in polyamory, both the partners are allowed to take multiple lovers or one lover. Polyamory means having multiple lovers and polygamy means having multiple spouses. Both are unconventional, uncommon practices in contemporary Western society.

poly·​am·​o·​rous ˌpä-​lē-​ˈa-​mə-​rəs. -​ˈam-​rəs. : involving, having, or characterized by more than one open romantic relationship at a time : marked by polyamory.

“Someone who is monogamous can date someone who is polyamorous; this is referred to as a mono-poly relationship,” explains Sullivan. In her experience, these relationships are one of the most difficult polyamorous relationship styles to maintain — however, they can work well with the right communication and boundaries.

Despite the shift in social and cultural acceptability of non-monogamy, marriage to multiple partners is currently illegal in all 50 states, and federal law still criminalizes marriage to more than one person. With the exception of Utah, polygamy is a third-degree felony punishable by both fines and imprisonment.