Primary custody refers to the parent with whom a child lives after both parents separate or divorce. It is also referred to as physical custody. Primary custody is awarded based upon a number of factors and doesn't necessarily denote the fitness of the parent. The primary residential parent generally has final decision-making authority in day-to-day care and control of each child. Primary custody is governed by state statutes, which vary by state.
The following is an example of one state's definition of primary custody:
"A parent has primary physical custody (or primary custody) of children for purposes of this rule if the children reside with the other parent for a period specified in the custody order of less than 30 percent of the year."