What are rules of order that modify or supplement parliamentary authority called?

The term referring to rules of order that modify or supplement parliamentary authority is known as special rules of order. These rules are created to address specific needs or situations that are not adequately covered by the general parliamentary authority, like Robert's Rules of Order.

Special rules of order allow organizations to tailor their procedures to fit their unique circumstances or preferences, ensuring that the governance structure is both effective and relevant to their particular needs. They can cover aspects such as voting procedures, meeting protocols, or the roles of committee members that may diverge from standard practices outlined in the overarching parliamentary authority.

In contrast, standing rules pertain to the routine operations of an organization and establish ongoing procedures that govern the day-to-day functioning. General rules are not a recognized category in parliamentary law and procedural rules typically refer to the framework of a specific meeting's conduct or agenda but do not serve the same purpose as special rules of order.