Rose Fox plans to spend this most romantic of evenings with the woman she calls her “girlfriend-in-law” — that is, her husband’s girlfriend. Why not? They’re friends, they love Wednesday night choir practice, and, of course, they both love Ms. Fox’s husband, Josh.

Josh will be home alone in Inwood, catching up (ahem) on his sleep. If his wife’s long-distance lover calls, however, he can always talk to her until his wife — or girlfriend, or both — comes home.

And that’s the beauty of polyamory. It’s so simple!

Polyamory is the name of the movement that promotes loving lots of lovers. For some reason, it also promotes a lot of potluck suppers. Go figure.

The movement is not to be confused with “swinging,” wherein icky people have sex with other icky people they’ll never see again (unless they’re being blackmailed on Long Island).

Nor is it to be confused with “cheating,” because polyamorous people are supposed to be completely honest about who’s doing what. And who. Some poly couples are so honest, in fact, that they share a calendar.

“It’s like being a soccer mom with three kids. ‘Can I take him to soccer? Can I make it in time for her ballet class?'” Ms. Fox said. “Except we’re adults.” And except it’s not soccer.

Ms. Fox runs a monthly meet-up that generally attracts about 10 of the poly curious. Hers, however, is not the only game in town.

Manhattan film and TV producer Justen Bennett-Maccubbin runs another discussion group, Polyamorous NYC, at the Lesbian, Gay, Bisexual & Transgender Community Center. His events attract a crowd of about two dozen people, many of whom, he’s proud to say, are “hipsters.”

And then there’s the Tri-State Poly group. “It’s a little bit more suburban-focused, more for people in their 40s and 50s,” Mr. Bennett-Maccubbin said. They meet for dinner at the Empire Szechwan.

Like other outsider groups before them, the polyamorous are trying to gain acceptance as painfully normal — even prosaic — people (which perhaps explains why they dine at the Empire Szechwan). They’ve even adopted a cute mascot: the parrot. Think “wanna cracker” and you’ll see why it represents the poly.

Mr. Bennett-Maccubbin, who is gay, realized he was polyamorous when, at 19, he dated his first couple. “It was infinitely more interesting!”

I’m sure it was. Ms. Fox had her own poly-revelation when she was 14, away at summer camp, and her boyfriend called to tell her he was dating someone else.

“My stomach fell like a rock,” she said. Then she realized her boyfriend wasn’t actually dumping her, just adding someone new. A lifestyle was born. It helped that she was raised in the Village.

Within polyamory, there are no limits on the number of people one can “date” (as the practitioners politely put it), or their sexual orientation. The slang tells it all. There are triads (groups of three), quads, “tribes,” and “TOCOTOX” — “TOo COmplicated TO eXplain.” There’s also the plaintive plea: “PWP” — Poly Wanna Potluck.

So, will this group some day become as accepted as, say, transsexuals?

“We’ve got the Bible going for us,” Ms. Fox said. The Good Book is filled with polyamorous husbands, at least. And it’s not like strict monogamy has had such a great run through civilization.

“I think most people, by their nature, are not monogamous,” Mr. Bennett-Maccubbin said. “If you look all the way up to President Clinton, monogamy is the exception, not the rule.”

Maybe that’s not the happiest thought to dwell upon this Valentine’s Day. But consider the lesson Ms. Fox learned one polyamorous Valentine’s Day a few years back.

“It was me and Josh and his then-still-wife and her boyfriend and his involvements and it went out from there — about eight or nine people,” Ms. Rose said. “We all went to the wine country for the weekend and the problem was: One person wasn’t feeling well. If you’re not well on Valentine’s Day, you probably really want your partner’s attention.”

The weekend fell apart as one lover couldn’t pay enough attention to the next lover, to the next, to the next, to the next. “It was a disaster,” Ms. Fox said. But she did learn one thing: “Attention is the currency of relationships.”

Pay enough attention to your beloved today — and forever — and he or she may never show up at a polyamorous discussion group. Or potluck.