In a system, what is referred to as the unit that plays a dominant role in its operation?

The concept of a unit that plays a dominant role in the operation of a system is best described by the term "core function." In any complex system, there is typically a central component or core function that governs how the system operates and performs its tasks. This core function is essential for the overall effectiveness of the system, as it is responsible for executing the main purpose of the system and directly impacts its functionality.

While "lead part," "operational unit," and "primary element" may seem relevant, they do not convey the same level of essentiality and systematic importance as "core function." The term "core function" denotes not just the primary operational mechanic, but also indicates the foundational activity that everything else in the system relies upon for supporting roles and interactions. Thus, the core function is a critical aspect of a system’s design and implementation, ensuring that all other components and aspects synergize to fulfill the intended objectives of the system effectively.