What term refers to the action part of a system when it accomplishes its intended purpose?

The term that accurately describes the action part of a system when it accomplishes its intended purpose is "Function." In the context of systems, a function refers to the specific task or role that a system is designed to perform. It embodies what the system is meant to achieve and how it operates to fulfill its purpose.

In contrast, while "processes," "operations," and "activities" can describe various aspects of system behavior, they are broader terms that do not specifically indicate the concept of fulfilling an intended purpose. Processes may refer to a sequence of actions or steps taken to achieve a particular end but do not exclusively capture the idea of accomplishing a designated function. Operations can denote the manner in which tasks are carried out, but again, this term lacks the precision that "function" provides regarding achieving specific objectives. Activities represent ongoing actions but do not necessarily imply successful completion of a system's purpose.

Understanding the distinction between these terms helps clarify the role each plays within a system and why "function" is the most fitting designation for the action part of a system that effectively achieves its intended purpose.