[Middle English tyrannie, from Old French, from Late Latin tyrannia, from Greek turanni, from turannos, tyrant.] 

[French démocratie, from Late Latin dmocratia, from Greek dmokrati : dmos, people; see d- in Indo-European roots + -krati, -cracy.] 

In anthropological theory, a chiefdom is a form of social organization more complex than a tribe, and less complex than a state (see Cultural_evolution). Chiefdoms are characterized by pervasive inequality of peoples and centralization of authority. At least two inherited social classes (elite and commoner) are present, although social class can often be changed by extraordinary behavior during an individual's life. A single lineage/family of the elite class will be the ruling elite of the chiefdom, with the greatest influence, power, and prestige. 

A single simple chiefdom is generally composed of a central community surrounded by or near a number of smaller subsidiary communities. All of these communities recognize the authority of a single kin group or individual with hereditary centralized power, dwelling in the primary community. Each community will have its own leaders, which are usually in a tributary and/or subservient relationship with the ruling elite of the primary community. 

A complex chiefdom (see Cahokia as an example) is a group of simple chiefdoms controlled by a single paramount center. Three levels of administration exist, rather than two. The local community has leaders that bow to the head of their chiefdom, who in turn serves a single paramount individual or kin group with centralized power. 

Chiefdoms have been shown by anthropologists and archaeologists to be a relatively unstable form of social organization. They are prone to cycles of collapse and renewal, in which tribal units band together, expand in power, fragment through some form of social stress, and band together again. 

the domain ruled by an emperor or empress; the region over which imperial dominion is exercised 
a group of countries under a single authority; "the British empire" 
a monarchy with an emperor as head of state 
conglomerate: a group of diverse companies under common ownership and run as a single organization 
An empire (also known technically, abstractly or disparagingly as an imperium, and with powers known among Romans as "imperium") comprises a set of regions locally ruled by governors, viceroys or client kings in the name of an emperor. By extension, one could classify as an empire any large, multi-ethnic state ruled from a single center. Like other states, an empire maintains its political structure at least partly by coercion.

Rule by a single leader who has not been elected and may use force to keep control. In a military dictatorship, the army is in control. Usually, there is little or no attention to public opinion or individual rights.