What defines a country that has complete control over its territory and no external governance?

The concept that defines a country with complete control over its territory and no external governance is sovereignty. Sovereignty reflects the ultimate authority of a state to govern itself without outside interference. This includes the power to enforce laws, conduct foreign affairs, and manage internal matters without external control or influence. A sovereign state typically has recognized borders, a permanent population, and a government that exercises control over its territory.

In contrast, a colony is typically subject to the governance of another country and lacks complete self-governance. While 'nation' refers to a group of people who share a common identity, such as culture or language, it does not inherently imply political control over a territory. The term 'state' refers to a political entity with defined borders and a governing body, but it does not specifically address the external relationships or control like sovereignty does. Therefore, sovereignty is the most accurate term for a country that operates independently and without external governance.