People talk about Monogamy vs. Polyamory/Consensual Nonmonogamy like it's a binary, like you're one or the other. I reject that notion.
Any binary requires two definite observable states, like on or off. That's the metrics. But with non-monogamy vs. monogamy, what are your metrics? Is it sex? Is it love? There are a lot of people who are asexual, don't have sex, but consider themselves polyamorous. Asexual polyamory is a real thing. There are a lot of swingers, folks in "the lifestyle," for whom it's all about sex and not developing feelings.
Of course, you have to define "monogamy." Some folks define monogamy so strictly that friends of the attracted to gender are forbidden. Other folks consider themselves monogamous if they don't have sex with people other than their partner, but are okay with kissing, cuddling, etc. And then, you have to define sex...
Monoamorous is a word and is aptly used in the realm of feelings, Monoamorous vs. Polyamorous. I would add in the realm of sex, Monosexual vs. Polysexual? Can a person be Polyamorous and Monosexual? I believe so but it's seldom talked about, except maybe as an "emotional affair." But, is it an affair if it's consensual?