Definition - What does Primary mean?
Primary is a term that is utilized in polyamorous relationships to indicate that one relationship or partner takes priority over any other relationships or partners. One may refer to their "primary partner," "primary," or their "primary relationship." Others who become involved with members of the primary relationship might be designated secondary partners and, in some cases, there may be restrictions on their involvement based on the agreements of the primary relationship.
Kinkly explains Primary
Not all polyamorous people utilize this terminology. Some find it problematic due to the way it designates certain partners as "less than" others. There are also different manners of usage for the term; some are descriptive, simply used to convey the nature of a relationship ("I live with Bob so he is my primary partner") and some prescriptive, where the term dictates how the relationship should function ("Bob is my primary so I should spend more time with him than Bill").