What would best describe a system element that cannot be further decomposed?

A system element that cannot be further decomposed is best described as elementary or atomic. This term indicates that the element is at the most fundamental level, meaning it represents a single unit that does not have any smaller components that can be identified or separated. In systems engineering, understanding the atomic nature of these elements is crucial because they serve as the building blocks for larger systems.

These atomic elements are essential for establishing clear boundaries and responsibilities within a system model, making them easier to manage and analyze. Recognizing an element as atomic facilitates a more straightforward understanding of how it interacts with other components and contributes to the overall function of the system.

In contrast, other terms like complex, complicated, and integrated describe different characteristics of systems or their elements but do not accurately convey the idea of indivisibility that is inherent in an elementary or atomic element.