Final answer:
A nation-state is characterized by sovereignty and a shared cultural or national identity, such as common language, ethnicity, or religion, among its citizens. This common identity unites the nation and allows it to operate with a central government without external control.
Step-by-step explanation:
A characteristic of a nation-state is sovereignty, which means that the nation-state has complete authority to govern itself without external interference. This concept of sovereignty aligns with the idea that a state must decide its own foreign and domestic policies without seeking direct authority from another nation. Additionally, nation-states often share a common cultural or national identity, typically involving a shared language, ethnicity, religion, history, or a combination of these elements, which helps to unite the government and the citizens.
The characteristic that often distinguishes a nation-state is that the majority of its citizens share a common identity. Therefore, the sense of nationalism and a united government are central to the definition of a nation-state, which can be seen in how European countries like Italy, Germany, and France have developed a strong sense of cultural unity among their populations.