Dispositors
A dispositor is a delineation of planetary rulership in relation to the signs. For instance if Mercury is in Libra, its dispositor is Venus, if Venus is in turn in Sagittarius, its dispositor is Jupiter, and if Jupiter is Cancer its dispositor is the Moon. This process continues until there is a final dispositor (sign in its own rulership) or it circles around in a never ending chain of command.
Read more about this topic: Domicile (astrology)