What practice involves the acquisition of territory beyond a nation's borders?

The practice that involves the acquisition of territory beyond a nation's borders is imperialism. This concept refers to the policy or practice where a country extends its power and influence over other nations through colonization, military force, or other means. Imperialism typically includes not only the physical takeover of land but also the political, economic, and cultural domination over the local populations.

By contrast, colonialism specifically refers to the establishment and governance of a colony in a foreign territory, which is often a component or outcome of imperialism, but does not encompass the broader aspects of influence associated with imperialism itself. Nationalism, on the other hand, focuses on the interests and culture of a particular nation or group, potentially leading to a push for independence rather than the acquisition of foreign territory. Altruism, while indicating a concern for the welfare of others, does not relate to territorial acquisition at all. Understanding these distinctions helps clarify why imperialism is the correct choice for the acquisition of territory beyond national borders.