A nation is a community of people formed on the basis of a combination of shared features such as language, history, ethnicity, culture and/or society. A nation is thus the collective identity of a group of people understood as defined by those features. Some nations are equated with ethnic groups (see ethnic nationalism) and some are equated with affiliation to a social and political constitution (see civic nationalism and multiculturalism). A nation is generally more overtly political than an ethnic group. A nation has also been defined as a cultural-political community that has become conscious of its autonomy, unity and particular interests.

The consensus among scholars is that nations are socially constructed and historically contingent. Throughout history, people have had an attachment to their kin group and traditions, territorial authorities and their homeland, but nationalism – the belief that state and nation should align as a nation state – did not become a prominent ideology until the end of the 18th century. There are three notable perspectives on how nations developed. Primordialism (perennialism), which reflects popular conceptions of nationalism but has largely fallen out of favour among academics, proposes that there have always been nations and that nationalism is a natural phenomenon. Ethnosymbolism explains nationalism as a dynamic, evolving phenomenon and stresses the importance of symbols, myths and traditions in the development of nations and nationalism. Modernization theory, which has superseded primordialism as the dominant explanation of nationalism, adopts a constructivist approach and proposes that nationalism emerged due to processes of modernization, such as industrialization, urbanization, and mass education, which made national consciousness possible.

Proponents of modernization theory describe nations as "imagined communities", a term coined by Benedict Anderson. A nation is an imagined community in the sense that the material conditions exist for imagining extended and shared connections and that it is objectively impersonal, even if each individual in the nation experiences themselves as subjectively part of an embodied unity with others. For the most part, members of a nation remain strangers to each other and will likely never meet. Nationalism is consequently seen an "invented tradition" in which shared sentiment provides a form of collective identity and binds individuals together in political solidarity. A nation's foundational "story" may be built around a combination of ethnic attributes, values and principles, and may be closely connected to narratives of belonging.