Final answer:
In partitioning a system, each piece is known as a subsystem, which helps manage complexity and allows for development of separate functionalities that can be integrated later.
Step-by-step explanation:
When a system is partitioned into pieces, each piece is referred to as a subsystem. The process of dividing a system into smaller parts helps in managing complexity, organizing code, and assigning separate tasks to different teams or individuals within a development process. For instance, in a large software project, each subsystem could represent a specific functionality, such as user authentication, data storage, or network communication, and these subsystems could be developed and tested independently before being integrated into the final product.