It's often used to form nouns that describe forms of government or systems of rule. For example:
* Democracy: Rule by the people
* Autocracy: Rule by one person with absolute power
* Theocracy: Rule by religious leaders
* Bureaucracy: Rule by officials and administrators
While "-cracy" primarily refers to systems of government, it can also be used to describe other forms of control or dominance:
* Technocracy: Rule by technical experts
* Patriarchy: System of society where men hold power
* Plutocracy: Rule by the wealthy
* Meritocracy: Rule by those with merit or talent
So, in essence, "-cracy" signifies a form of rule, control, or dominance by a specific group or entity.