In 22nd, 23rd and 24th century terms, a colony refers to a group of people settling on an uninhabited planet. These settlements are normally small in size and supported by a government. Most colonies are civilian in nature. The term used when a colony is set-up is called colonization.
The United Federation of Planets encourages colonization. The Federation Council accepts petitions from citizens looking to colonize another world. Both the Federation and Starfleet actively search for planets for colonization, and the Council must approve planets suitable for colonization before allowing settlers to move there. Usually no more than a few hundred settlers move to any given starting colony.
- It remains unclear whether, in the Federation, colonies are part of a larger government, i.e. a parent planet holds responsibility for them, or are autonomous, i.e. no parent planet holds responsibility for them. It would seem most likely most colonies remain under the umbrella of a larger government, as Jean-Luc Picard mentions in Star Trek: First Contact that only 150 members exist in the Federation. Most colonies would probably be self-determining, i.e. local issues would be dealt with by locals. Some colonies have ceded from the Federation due to various issues or treaties.