Kids are pattern-matchers. They will notice who's around, who stays over, and who gets a key long before they have the vocabulary for it — and if you haven't named it for yourself, you'll improvise the explanation in a moment you didn't choose. This is the M of 📝The FAMILY Framework: Map the Structure Before They Ask.
Settle Your Own Words First
The work here isn't teaching your kid terminology. It's making sure you have language you can say out loud without hesitating, because hesitation is the part they read. The terms below are the ones I use; the broader map of structures they sit inside is in 📝Ethical Non-Monogamy: Relationship Structures.
Nesting partner — the partner I live with, share a household and daily logistics with.
Primary, held loosely — I use hierarchy, but as a description of practical reality rather than a ranking of who I love more. Who's home for bedtime. Who's on the emergency contact list. That's what the word is doing.
Metamour — my partners' other partners, who I may or may not have a relationship with myself.
Partner — anyone I don't need a modifier for, which is most of them, most of the time.
Kids Don't Need the Vocabulary Lesson
They need consistency between what you call people and how those people actually show up. A child who hears "my partner" and watches that person appear every Tuesday, remember their birthday, and still be there in a year has learned everything the word was ever going to teach them. A child who hears a carefully chosen term attached to someone who drifts in and out has learned something too, and it isn't about polyamory.
So the test for your vocabulary isn't precision. It's whether the words match the pattern your kid is already tracking.
What This Is Not
It isn't a disclosure. Naming your structure to yourself is preparation; what you actually say to a child is governed by their age and their question, which is its own domain. And it isn't a promise that the structure won't change — you'll rename things, people will move in and out of those categories, and the terms will need revisiting. Do that revisiting on your own time rather than in front of your kid, and the change lands as ordinary rather than as an event.
I keep my own working glossary of these terms private, and I'd recommend anyone doing this write theirs down somewhere nobody else reads. The point of putting it on paper isn't the paper. It's finding out which of your words you don't actually believe yet.