Polyamory refers to the practice of having more than one romantic or sexual relationship or other personal social involvement, either committed or casual, at a time, usually specifically with the consent of all relationship participants to this arrangement. Some relationships may have a greater level of commitment or investment of resources than others, causing them to be regarded as the "primary" relationship, with all other relationships being "secondary." A couple raising children and living together would reasonably be considered "primary" compared to a long-distance relationship that does not involve children or shared finances. Not all polyamorists adopt these labels for their relationships, but the polyamory community online collectively agrees that there is clearly a greater level of commitment involved in cohabitation, shared finances, and raising children together.

The most common form of ethical polyamory is the "couple-plus" relationship model: two partners are committed in involvement with each other, but they choose to open the relationship so that one or both of them may be involved with an additional partner or partners. The additional partner(s) may be treated as an equal member of the original couple, forming a 'closed polygon,' such as a triad or tetrad of people all mutually involved with each other. It is far more common, however, for the additional partner(s) to only be involved with one member of the couple and to be treated as entirely outside and separate from the couple's committed relationship: this outside relationship is usually regarded by the couple as 'secondary' in both importance and personal investment, compared to the 'primary' relationship between the couple.

Some polyamorists oppose the primary-secondary relationship dynamics, perhaps subscribing to relationship anarchy and feeling that these dynamics create atmospheres of inequality, privilege, and marginalization between various partners. Other polyamorists may simply prefer to live with a strong focus on personal autonomy and limited entanglements in their lives, avoiding "settling down" and any arrangement which would force them to be beholden to another person financially or logistically. Somebody with any of these preferences and attitudes may elect to perform solo polyamory, also called solitary polyamory, as a way to maintain personal free agency and to avoid the imbalances of ranked relationships.

Solo polyamory, as a clearly defined and labeled sub-community among polyamorists, has existed since 2014, and it is increasingly widely adopted, especially among relationship anarchs and asexual or aromantic polyamorists. It is considered by some asexual and aromantic polyamorists to be a good way to protect one's own interests during the early stages of a new relationship, when a prospective partner may decide that they require a more sexual and romantic relationship dynamic than one is willing or able to provide.

A solitary polyamorist will usually live separately from all partners, even if they elect to stay within easy visiting range. They will usually maintain finances independently as well, and while some solitary polyamorists may certainly have children with their partners, the arrangement for raising the children may involve any variation of custody and cohabitation for the child with a parent or any of the parents' other partners. A solo polyamorist may have only casual relationships, only committed relationships, or a mix of these. They may maintain long-distance relationships along with geographically local relationships, and sometimes a polyamorist will be functionally solitary due to being far away from all partners during business trips or years spent at university.

Some solo polyamorists are involved in a complex 'polycule' involving more than one network of relationships to people who are not all mutually involved in one another's relationship networks. In such circumstances, solo polyamory can allow a very committed polyamorist to move freely and easily between the domestic environments of more than one group of partners, not unlike two households transferring custody of a child between them from week to week. In this way, the solitary partner may depend on each household for financial and domestic resources, rather than maintaining an independent residence from all of them, but he remains mobile and independent of any single household as a permanent living situation.

Iron Noder Challenge 2014, 7/30