Nationalism is best defined as:

Nationalism is fundamentally a political ideology that associates the concepts of the nation and the state, emphasizing the unification of a particular group of people—often defined by shared characteristics such as language, culture, ethnicity, or history—into a sovereign political entity. This ideology promotes the interests and culture of the nation, often prioritizing it above foreign influences or interests.

In this context, nationalism advocates for self-governance and the promotion of national interests, which is why identifying it as a connection between nation and state aligns with the essence of nationalism. It underlines the importance of sovereignty and a collective identity among people who share a common national background.

The other definitions do not capture the essence of nationalism in the same way. For instance, a sense of global unity implies collaboration and harmony between different nations rather than a focus on a specific national identity. Cultural appreciation emphasizes the acknowledgment and respect for diverse cultures but does not necessarily align with the nationalistic agenda. Lastly, acceptance of multiculturalism focuses on coexistence among various cultures within one society, which can contrast with the more exclusionary tendencies that sometimes accompany nationalism.