A private citizen is a citizen who does not have an official or professional role in a given situation.
The same person may be a private citizen in one role, and an official in another. For example, a legislator is an official when voting in the legislature, but a private citizen when paying taxes or when undertaking a citizen's arrest in a public place.
A private island is a disconnected body of land wholly owned by a private citizen or corporation. Although this exclusivity gives the owner substantial control over the property, private islands remain under the jurisdiction of national and sometimes local governments. Their size can vary widely, from that of a typical suburban yard to several hundred square kilometers.
A citizen's arrest is an arrest made by a private citizen – a person who is not acting as a sworn law-enforcement official. In common law jurisdictions, the practice dates back to medieval England and the English common law, in which sheriffs encouraged ordinary citizens to help apprehend law breakers.