The umbrella term of "consensual non-monogamy" covers everything from the casual sex of swingers to the loving, long-term relationships of polyamorists. If it involves more than two people, sex or love, and everyone has consented, then it's CNM.
These relationships are more common than you likely think. Research shows something like 5% of Americans are involved in this type of arrangement at any given time and about one in five has engaged in some form of consensual non-monogamy in their lifetime.
"My colleagues and I joke around that this is equivalent to the number of people who own a cat," said Heath Schechinger, a UC Berkeley psychologist and co-chair of the American Psychological Association's task force on CNM. "You likely have friends and colleagues who are doing this, but you just don't know about it."
These relationships are also more normal than you probably imagine. Unflattering stereotypes of polyamorists as damaged, dysfunctional, or secretly coerced by pushy partners are all belied by research.
"Comparison studies looking at all of the gold standards for measuring relationship quality — relationship satisfaction, sexual satisfaction, duration of the relationship, communication, etc. — show that consensually non-monogamous relationships perform equal or better than monogamous relationships," Schechinger said.
Monogamy and non-monogamy may be similar in terms of outcomes and the demographics of participants, but it's still true that CNM relationships tend to have unique habits that many folks involved in traditional monogamous pairings could benefit from.