Aristocracy Rule by a small group (such as a high council).
Autocracy Rule by a single individual who wields unlimited power. While an emperor may rise to power due to hereditary lines, but is referred to as an autocrat rather than a monarch because his power overshadows his bloodline.
Democracy Rule by representatives elected by the population. An abstract form of polity.
Monarchy Rule by one individual who attains position because of hereditary lines.
Ochlocracy Rule by organized crime. Usually several factions or cartels rise to power and balance each other through conflict and cooperation.
Oligarchy Rule by a small group wielding virtually unlimited power for evil or selfish goals. Oligarchy and plutocracy often overlap.
Plutocracy Rule by the wealthy. The upper classes completely control all laws and government positions.
Polity Rule by the people. Every law and decision are put to a vote. This is the truest form of democracy, but only works in a limited fashion over small populations.
Provincial Rule by the provinces (or other territorial breakdown). A provincial government is one in which each village or other unit of area rules itself and there is no central government.
Theocracy Rule by the church. In this case, church and state are virtually one. Priests hold political offices and adherence to the religion is required for citizenship.
Bureaucracy Government by departments, rule being through the heads of various departments and conducted by their chief administrators. Confederacy: Government by a league of (possibly diverse) social entities so designed as to promote the common good of each other. Democracy: Government by the people. Citizens elect government representatives.
Dictatorship Government whose final authority rests in the hands of one supreme head. Usually a military leader.
Feodality Government by layers where each successive layer of authority derives power from the one above and pledges fealty likewise. A lot of Monarchies are feudal in nature.
Gerontocracy Government reserved to the elderly or very old.
Gynarchy Government reserved to females only.
Hierarchy Similar to a Feodality but religious in nature.
Magocracy Government by magic-users only.
Matriarchy Government by the elder females.
Militocracy Government by the armed forces.
Pedocracy Government by the learned, scholars and savants.
Republic Government by representatives of an established electorate who rule on behalf of the electors.
Syndicracy Government by a body of syndics, each representing some business unit.