The below is a brief outline of the term theological triage*.
First-order doctrines are those that are fundamental and essential to the Christian faith.
Second-order doctrines are those which are essential to church life and necessary for the ordering of the local church, but which, in themselves, do not define the Gospel.
Third-order doctrines are those which may be the ground for fruitful theological discussion and debate, but which do not threaten the fellowship of the local congregation or the denomination.
*Definition pulled from Part III - The pastor and theological triage