Established heading:

A heading that is authorized for use in other MARC records as a main entry (1XX), added entry (700-730), or series added entry (440 or 800-830) field or as the lead element in a subject access (600-655; 654-657) field.

In authority records, established headings are used in fields 100-155 (headings) and fields 500-555 (tracings) for established heading records [code a (Established heading record) or code f (Established heading and subdivision record) in 008/09, Kind of record].