What distinguishes functional requirements from non-functional requirements?

The distinction between functional requirements and non-functional requirements is primarily based on what each category focuses on within a system. Functional requirements define the specific behaviors, functionalities, and interactions of a system from the user’s perspective. They detail what a system should do; for example, they may specify features like user authentication, data entry, processing transactions, or generating reports. These requirements are centered around user needs and the tasks that a system must perform to fulfill those needs.

Non-functional requirements, on the other hand, specify criteria that judge the operation of a system rather than specific behaviors. They assess the quality attributes of the system, such as performance, reliability, scalability, usability, and security. Essentially, while functional requirements describe "what" the system should do, non-functional requirements focus more on "how" the system should perform its operations and the qualities it must possess.

This understanding helps in effectively communicating the different aspects of system requirements and ensuring that both user needs and system quality are considered in the development process.