Mono/poly describes a relationship structure in which one partner practices polyamory and the other is monogamous by preference or orientation. The monogamous partner does not have or desire additional partners while their polyamorous partner has or maintains other relationships. The term acknowledges that this is not simply hierarchical polyamory with a primary who happens not to date others — it names the intentional mismatch of relational orientations as a structure with its own particular dynamics.
Mono/poly relationships are often described as uniquely challenging because they require partners to hold genuinely different orientations toward partnership without either one being wrong. The polyamorous partner's additional connections are not a gap to be filled or a phase to be resolved — they are an expression of how that person loves. The monogamous partner's preference for their own exclusivity is equally real. The structure asks both people to hold that difference simultaneously, indefinitely, rather than converging on a shared approach.
The dynamics of a mono/poly arrangement are distinct from those of a couple where both partners are polyamorous and one happens not to have other connections at a given time. When both people identify as polyamorous, there is a shared framework; the monogamous-by-circumstance partner could have other relationships if they arose. In a mono/poly structure, the monogamous partner is not waiting for the right person to come along — they are actively choosing monogamy as their relational mode while their partner is not. That difference in orientation is the structure.
The challenge most frequently discussed in mono/poly arrangements is the asymmetry of experience. The polyamorous partner is present for the emotions and commitments of multiple relationships. The monogamous partner is present for the emotions of one relationship, which includes being present for their partner's attention, energy, and time being shared in ways the monogamous partner does not share in return. Some people in mono/poly structures find that asymmetry workable and even comfortable. Others find it persistently painful regardless of goodwill on all sides.
Mono/poly structures are not inherently unstable or inherently a compromise. Some people in these arrangements describe them as genuinely fitting — a monogamous person who is not looking for additional partners themselves but who is not threatened by their partner's connections, or a polyamorous person whose partner's preference for exclusivity on their own side does not feel limiting. Whether the structure works depends on the specific people, their specific orientations, and their specific circumstances.
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definition contributed by Tessakin