Definition - What does Primary Relationship mean?
In a polyamorous relationship, the primary relationship takes priority and receives the most attention and resources. Generally, although not always, the primary relationship is the relationship that has lasted the longest or has the strongest bond.
Kinkly explains Primary Relationship
There can be many relationships that exist in a polyamorous relationship. A primary relationship is one in which a couple attend to their own sexual and emotional needs as a priority over any additional relationships.