What Is Monogamy? Meaning, Types and Why It Is a Choice
Monogamy means having one romantic and sexual partner at a time, usually by mutual agreement between two people. It is the default relationship model in the US, Canada, the UK and most of Europe, and for many couples it is a deeply happy one. It is also a choice, and couples who treat it as one, rather than an assumption, tend to keep it better.
The word looks simple, but people mean at least four different things by it, and most couples never say out loud what their version includes. Below: the meaning, the types, the unwritten rules, how it compares with polygamy, and why choosing monogamy on purpose matters.
Monogamy meaning: where the word comes from
"Monogamy" comes from the Greek monos, one, and gamos, marriage. For most of its history it meant being married to one person, as opposed to being married to several at once. Over time the meaning shifted from marriage to sex and love. Today, most people use it to mean "only each other".
Two related words:
- Monogamous is the adjective: "a monogamous couple", "I've always been monogamous."
- Non-monogamy is anything that is not one partner at a time. Our page on non-monogamy meaning explains that side.
The types of monogamy people mix up
When biologists and sociologists say monogamy, they split it into kinds. The split is useful for ordinary couples too, because it explains a lot of arguments.
Social monogamy
Two partners live as a pair: they share a home, raise children, show up together at weddings. It says nothing about whether either has ever strayed. In biology, a "monogamous" bird species is usually socially monogamous.
Sexual monogamy
Neither partner has sex with anyone else. This is what most people mean when they say "we're monogamous".
Emotional monogamy
Neither partner falls in love with, or builds deep romantic intimacy with, anyone else. Some couples care more about this than about sex. "I could forgive a drunken kiss, but not a year of secret texts" is an emotional-monogamy rule.
Genetic monogamy
All children in the pair are biologically the couple's own. This mainly matters to biologists studying animals, and it is where the big surprises turn up. More on that in is monogamy natural.
Lifelong vs serial monogamy
Lifelong monogamy is one partner for life. Serial monogamy is one partner at a time, but several over a lifetime, one after another. That second pattern is a very common way to live in Western countries today. Our page on serial monogamy looks at it properly.
Monogamy in a relationship: the rules nobody writes down
Here is the part the dictionary skips. Two people can both say "we're monogamous" and mean quite different things.
Is it cheating to:
- flirt at a work party?
- keep chatting to an ex?
- have a dating app on your phone "just to look"?
- watch porn?
- slow dance with a friend?
- have a close friendship with someone you once fancied?
Couples answer these very differently, and most never ask. Then one day someone crosses a line the other person thought was obvious.
A simple exercise helps. Each of you writes your own list, privately: things that are fine, things that are grey, and things that are a definite no. Then compare. You will probably agree on most of it. The surprises are where the useful conversation lives.
If your lists differ, that is not a warning sign. Take Nadia and Tom, an invented couple: she thought staying close to an ex was harmless, he thought it was the one thing that would hurt. Ten minutes of talking turned a future row into a simple agreement, she keeps the friendship and he gets invited along now and then.
Plain words to start it: "I realised we've never actually said what monogamy means for us. Can we each write a list and compare? I'm not worried about anything, I'd just like us to be on the same page."
Monogamy vs polygamy: what is the difference?
Monogamy is one partner at a time. Polygamy is marriage to more than one spouse at once. It comes in two forms:
- Polygyny: one man with more than one wife. This is the form found in most places where polygamy is legal.
- Polyandry: one woman with more than one husband. Much rarer.
Marrying a second spouse while married, called bigamy, is illegal across the US, Canada, the UK and the EU. Relationships between consenting adults are not. That is general information, not legal advice.
Polygamy is also different from polyamory, which is about honest, loving relationships with more than one person, usually without any marriage involved. Our page on polyamory vs polygamy untangles the two.
Is monogamy only in humans?
No, but it is rarer in nature than people assume. True social monogamy is common in birds and rare in mammals: it is often quoted as under 10 percent of mammal species. And when scientists ran genetic tests on socially monogamous birds, they often found chicks fathered by a male outside the pair.
So the swan on the wedding card is a lovely symbol, and a slightly optimistic one. What that does and does not tell us about humans is a bigger question, covered in is monogamy natural.
Why monogamy is a choice, and a valid one
Many couples never choose monogamy. They simply arrive in it, because it is what everybody does. That is a pity, because a chosen agreement is stronger than an assumed one.
Choosing monogamy means you have looked at the alternatives, at least in your head, and decided this is what you both want. It means you can talk about attraction to other people without panic, because noticing someone is not the same as acting on it. And it means the agreement belongs to you, not to your parents, your friends or a film.
Monogamy has real strengths: simplicity, focus, fewer calendars, a clear sense of what you have promised. For plenty of people it is exactly right, and nobody should feel pushed out of it.
It also has a well-known challenge. Long-term couples often find desire fades as closeness grows. Esther Perel's Mating in Captivity (2006) is the classic book on that tension: her idea, roughly, is that desire needs a little distance and mystery, while love wants closeness. If that rings true, our guide on how to spice up your marriage has ideas that keep the agreement intact.
The same goes the other way. Some couples talk it through and realise one or both of them wants something different. The relationship escalator is a useful idea here: the default path of dating, moving in, marriage and children, which works beautifully for some and feels like a conveyor belt to others.
How to have the monogamy conversation
You do not need a crisis to talk about this. A calm evening and a few honest questions are enough.
- What does monogamy mean to each of us? Use the list exercise above.
- What would we do if one of us developed a crush? Agree in advance that saying so is safer than hiding it.
- Is there anything we are curious about but have never said? No pressure to act on any of it.
- When do we check in again? Once a year is fine. Agreements age.
It helps a great deal to have friends you can talk to about this honestly, without anyone flinching. Open-minded does not have to mean open: in our own circle, a first meeting is just a coffee or a dinner, and nobody assumes anything about what a couple's agreement is.
Choosing what fits
Monogamy is a real choice with real rewards, and so are the alternatives. The healthiest couples we know, whatever their agreement, are the ones who talk about it openly and keep talking. If you would like to spend time with people who are relaxed about these conversations, you can join Rope & Candy. It is free, it takes one email, and when someone from our team is in your city, we meet you for a coffee or a dinner. Nothing is expected after.
Questions people ask
What is monogamy in a relationship?
It is an agreement between two partners to be each other's only romantic and sexual partner. What counts as breaking it, from flirting to a kiss, varies from couple to couple, which is why it helps to say it out loud.
Is monogamy only in humans?
No. Many bird species pair up for a season or for years, and a small minority of mammals do too. Genetic testing shows that even socially monogamous birds often raise some young fathered outside the pair.
What is a polygamist relationship?
Polygamy is marriage to more than one spouse at once. Usually it means one man with several wives, called polygyny. It is illegal across the US, Canada, the UK and the EU, though legal in some other countries.
Is monogamy better than non-monogamy?
Neither is better in general. Research by Conley and colleagues found similar relationship satisfaction in consensually non-monogamous and monogamous relationships. What matters is that both partners actually chose the agreement they live in.