What term describes the assumption that one value system is superior to another?

The correct term that describes the assumption that one value system is superior to another is ethnocentrism. Ethnocentrism refers to the tendency of individuals to evaluate other cultures or belief systems primarily through the lens of their own cultural norms and values. This perspective often leads to viewing one's own culture as the standard by which others should be measured, thereby fostering prejudices and misunderstandings about different cultures.

In contrast, acculturation describes the process of one cultural group adopting the traits of another, while cultural pluralism emphasizes the coexistence of diverse cultural groups within a society, valuing their unique contributions rather than ranking them. The term superiority, although it might relate to feelings regarding cultural value, does not specifically encapsulate the idea of comparing different cultural value systems, which is central to the concept of ethnocentrism. Thus, ethnocentrism is the most precise term among the choices given for describing the belief in the superiority of one value system over another.