Ethical non-monogamy

What is ethical non-monogamy?

Ethical non-monogamy (Dutch: ethische non-monogamie), usually abbreviated to ENM, is the umbrella name for relationship forms in which someone has more than one sexual or romantic bond and everyone involved knows about it and consents to it. The word ethical points to exactly that: openness beforehand, not the form itself. Without that consent it is called cheating.

What ethical non-monogamy means in practice

It is not a relationship form but a category, and that is the most commonly made mistake.

Roos Reijbroek describes it in Systeemtherapie as an umbrella term for many different ways in which people live non-monogamously and have made agreements about it with each other. Under that umbrella stand forms that resemble one another very little.

Two examples that show the difference. A couple agrees that they go to a swingers club together and play with others there, but that nothing happens outside those evenings and that no phone numbers get exchanged. That is swinging: the non-monogamy sits in a bounded setting, and the romantic exclusivity stays intact.

Another couple agrees that both may build a second relationship, with feelings involved, and that they keep each other informed about how those relationships are going. That is polyamory: here it is the romantic exclusivity that has been let go, while the sexual agreements may be stricter than for the first couple.

Both fall under ENM. Whoever mistakes the umbrella for one of the forms is talking past the other. That happens often.

Which forms fall under ethical non-monogamy

Four, and they differ on the question of what exactly gets shared.

1. Swinging. Reijbroek describes it as having sex together in specific settings (such as at a swingers club or with another couple). Sex outside the relationship, usually together and in a bounded context.
2. The open relationship. Partners allow each other to have sexual and/or romantic contacts alongside the partner relationship. Unlike with swinging, that often happens separately.
3. Polyamory. Entering into multiple meaningful connections or relationships. Here it is about feelings and not only about sex.
4. Relationship anarchy. The starting point that every connection in someone’s life is important and so no moral hierarchy is made. No fixed rank between partner, friend and lover.

The boundaries run into each other. A couple can swing and also have an ongoing bond with someone else, where none of the four words exactly covers what they do and they use none of them themselves. Labels are rarer here than the literature suggests.

Where the word ethical non-monogamy comes from

From the movement itself, and later than people think.

The framework was popularized by The Ethical Slut by Dossie Easton and Janet Hardy, released in 1997 by Greenery Press. The encyclopedia entry mentions well over two hundred thousand copies sold and the nickname “the poly bible.” Easton and Hardy met in 1992 through the Society of Janus, a BDSM organization, which explains why the vocabulary of consent in both worlds resembles each other so closely.

The book did not coin the phrase ethical non-monogamy. It laid down the ethical framework, and the term grew afterward within the community. The word polyamory does have a traceable inventor: Morning Glory Zell, in 1990.

The book has also been criticized. Researcher Andrea Waling points out that the idea of a scarcity economy oversimplifies, that monogamy comes off too negatively, and that it makes “universal assumptions about people’s experiences.” Whoever reads it as a manual reads it wrong; as a document of its time it holds up.

How often ethical non-monogamy occurs

More often than the stigma would suggest, though the hard figure comes from the United States.

M. L. Haupert and colleagues put the same question to two national samples of single Americans and published that in The Journal of Sex & Marital Therapy. In the first sample (3,905 people) 21.9 percent said they had at some point been in a consensually non-monogamous relationship; in the second (4,813 people) 21.2 percent. Well over one in five.

The most striking part is in what did not matter. Almost everything. The percentage did not differ by age, education, income, religion, region, political preference or background. It did differ by sex and by sexual orientation: men reported it more often than women, and gay, lesbian and bisexual participants more often than heterosexual ones.

A Dutch population figure I have not found. So do not carry the American number over to the Netherlands one to one; what it does show is that this is not a fringe phenomenon of one subculture.

Why people choose ethical non-monogamy

For a range of reasons, and the research is firm that it does not come at the cost of what people get out of their relationship.

That last point is measured most sharply in a meta-analysis by Joel Anderson and colleagues in The Journal of Sex Research. They brought together 35 studies, good for 24,489 participants, and found no difference: monogamous and non-monogamous people report the same relationship satisfaction and the same sexual satisfaction. That held within the subgroups too, so regardless of whether it was an open, polyamorous or monogamish arrangement, and regardless of whether you looked at trust, commitment or intimacy.

What it delivers per person involved differs:

• For whoever takes the initiative, the gain is usually room: being able to explore something without having to give up the existing relationship.
• For the partner who goes along, the return more often sits in what the conversation itself brings up. To be able to agree on this, you have to say out loud what you want, and for many couples that is the first time it gets this concrete.
• For a couple together, the assumption that one person has to supply everything disappears. That is exactly what people who do it name as the gain.

That equal average says nothing about your relationship, meanwhile. A meta-analysis measures groups, not couples. Whoever starts this to solve a problem that is already there usually just relocates the problem.

What people get wrong about ethical non-monogamy

“That is cheating with a nice word.” The difference is the only thing that counts: with ENM everyone knows and everyone has consented. Sprott and Schechinger sum up CNM in The Family Psychologist as “an agreed-upon, sexually non-exclusive relationship.” The words agreed-upon are the whole definition.

“Monogamous couples are happier.” The meta-analysis by Anderson and colleagues found, across 35 studies and nearly 25,000 people, not a single difference, not in relationship satisfaction and not in sexual satisfaction. There was also no sign of publication bias, so it is not a matter of favorable outcomes getting published more often.

“People who do this are not bothered by it.” They are, but by the surroundings. Sprott and Schechinger state that “more than half of CNM-identified individuals have experienced anti-CNM discrimination in some form,” and that the accompanying minority stress goes together with more reported low mood and anxiety. The harm sits in the stigma, not in the relationship form.

“That stigma is not so bad.” Rhonda Balzarini and colleagues studied that among 641 people for Frontiers in Psychology. As long as you offer “non-monogamous” as one category, even non-monogamous participants judge monogamous people more favorably. But as soon as you name the forms separately, that largely disappears: then they rate their own form just as highly as monogamy. The halo effect around monogamy, described by the researchers as “a cognitive bias in which an individual is rated positively based on a single attribute,” therefore hangs partly on the label.

What you can do if this makes you curious

• Start with the question of what exactly you want, not with which word fits it. Sex, falling in love, attention and adventure each call for a different agreement.
• Say it out loud before anything happens. The order is the whole difference between this and cheating.
• Agree on what you report back. Everything, only the broad strokes, or nothing: all three work, provided it is settled beforehand.
• Put a moment in the calendar to review it. An agreement you never discuss again has, six months on, turned into a different agreement without anyone having said so.
• Do not do this to repair something. If something is already off now, it will not get less off from this.
• Take the surroundings into account. The stigma has been measured and it is real; who you share this with is a separate decision.

More reading about ethical non-monogamy

Within this glossary, polyamory, swinging and monogamy go deeper into the individual forms, and compersion explains what the opposite of jealousy means in this context.

Beyond this site, the article by Roos Reijbroek in Systeemtherapie is the most useful Dutch-language piece: it is written for therapists, but it describes the forms more precisely than most popular sources. Whoever wants to read the figures themselves will find the meta-analysis by Anderson and colleagues and the prevalence study by Haupert and colleagues.

Where this fits on this site

Many women and couples who approach me are busy with something like this without having a word for it. Sometimes the question is whether a third person can join, sometimes whether one evening with someone else fits within the agreement. What that means for a date with me, and how we go over it beforehand, is on the page about couples.

Sources

• Prevalence of Experiences With Consensual Nonmonogamous Relationships: Findings From Two National Samples of Single Americans. M. L. Haupert, Amanda N. Gesselman, Amy C. Moors, Helen E. Fisher & Justin R. Garcia, Journal of Sex & Marital Therapy 43(5), 424–440, 2017 (DOI 10.1080/0092623X.2016.1178675). Two quota samples of singles based on the American census. Provides the participant numbers 3,905 and 4,813, the percentages 21.9 and 21.2 for ever having had a consensually non-monogamous relationship, the finding that this did not vary with age, education, income, religion, region, political preference or background, and that it did vary with sex and sexual orientation.
• Countering the Monogamy-Superiority Myth: A Meta-Analysis of the Differences in Relationship Satisfaction and Sexual Satisfaction as a Function of Relationship Orientation. Joel R. Anderson, Jordan D. X. Hinton, Alena Bondarchuk-McLaughlin, Scarlet Rosa, Kian Jin Tan & Lily Moor, The Journal of Sex Research 63(1), 130–142, 2026 (DOI 10.1080/00224499.2025.2462988). Meta-analysis across 35 studies with 24,489 participants together. Provides the null results for relationship satisfaction and sexual satisfaction, the finding that they did not vary by sample characteristics, arrangement type or satisfaction dimension, and that there was no sign of publication bias. The publisher’s site blocks automated access; the abstract was read through Europe PMC and that link is above.
• Dimming the “Halo” Around Monogamy: Re-assessing Stigma Surrounding Consensually Non-monogamous Romantic Relationships as a Function of Personal Relationship Orientation. Rhonda N. Balzarini, Erin J. Shumlich, Taylor Kohut & Lorne Campbell, Frontiers in Psychology 9, 894, 2018 (DOI 10.3389/fpsyg.2018.00894). Study among 641 participants. Provides the description of the halo effect as “a cognitive bias in which an individual is rated positively based on a single attribute,” and the finding that the effect largely disappears once the individual relationship forms are judged separately instead of as one category.
• Consensual non-monogamy: A brief summary of key findings and recent advancements. Richard A. Sprott & Heath Schechinger, The Family Psychologist, published by Division 43 of the American Psychological Association, April 1, 2019. Provides the broad definition “an agreed-upon, sexually non-exclusive relationship,” the finding that more than half of the people who identify as CNM have experienced some form of discrimination, and the link between the accompanying minority stress and higher self-reported low mood and anxiety.
• Consensuele non-monogamie in de spreekkamer. Roos Reijbroek, Systeemtherapie 37(2), 2025. The Dutch-language professional article that names the forms. Provides the description of CNM as an umbrella term for many different ways in which people live non-monogamously and have made agreements about it with each other, and the descriptions of swinging, the open relationship, polyamory and relationship anarchy adopted on this page.
• The Ethical Slut. Encyclopedia entry about the book by Dossie Easton and Janet Hardy, Greenery Press 1997, with later editions in 2009 and 2017. Provides the year of publication and the publisher, the print run of well over two hundred thousand copies, the nickname “the poly bible,” the authors meeting through the Society of Janus in 1992, and Andrea Waling’s criticism of the scarcity idea and of the “universal assumptions about people’s experiences.”

Related terms

Ethical non-monogamy is the umbrella; the forms under it each have their own page.

• Polyamory. Multiple love relationships at once, with everyone’s knowledge.
• Swinging. Sex outside the relationship in a bounded setting, usually together.
• Monogamy. The opposite, and the norm the stigma hangs on.
• Compersion. Feeling pleasure at what your partner experiences with someone else.
• Metamour. Your partner’s partner, and what that relation does to you.
• NRE. The infatuation rush of a new bond, and why it affects the existing relationship.
• Relationship anarchy. The form that goes furthest: no rank between kinds of bonds.
• Ambiamorous. The word for the middle ground, for whoever fits both forms equally well.