Chapter

The Chapters or Chapter Houses of Gallifrey were the political affiliations of the various Great Houses and Families.

Overview
There appear to have be six chapters (DW: The Ancestor Cell) each representing one of the founders of Time Lord society. Each Chapter had its own dominant colour, and wore robes of that colour during ceremonial occasions such as the inauguration of a new Lord President. The most prominent were the Prydonian Chapter. The Doctor belonged to this chapter. Additionally, more Lord Presidents came from this one chapter than any other. (DW: The Deadly Assassin).

Its significance was closely followed by the Arcalian Chapter and the Patrex Chapter. The remaining three, the Dromeian Chapter, the Cerulean Chapter and the Scendles Chapter were overshadowed by the former. (source?)

The heads of the Chapters were the Lord Cardinals, and the chief of these in a chapter was known as the Cardinal Prime (NA: Lungbarrow) Both Lenadi and Borusa served as Cardinal Prime of the Prydonian Chapter.

The colour gold was reserved for the Gold Usher (DW: The Deadly Assassin)

According to Commander Hallam, marriage was a way of strengthening the bonds between Houses and Chapters. (BFG: Spirit)

Founders
According to legend there were six founders of the Chapters and modern Gallifreyan life.

and one other, possibly Eutenoyar (PDA: The Infinity Doctors, EDA: The Ancestor Cell)
 * Rassilon
 * Omega
 * Pandak
 * The Other
 * Apeiron

List of chapters

 * Prydonians
 * Arcalians
 * Patrexes
 * Dromeians
 * Ceruleans
 * Scendles

Ceremonial colours
Prydonians used scarlet and orange. Arcalians used green. Patrexes used heliotrope (a shade of pinkish purple). (DW: The Deadly Assassin) Dromeians used silver-gray and Ceruleans, as the name would indicate, used blue. (NA: Lungbarrow) The colours used by the Scendles remains unknown.