Functional vs Non-Functional Requirements

Summary

Functional requirements describe what a system should do (specific behaviors); non-functional requirements describe how it should perform (speed, security, usability) — both are essential, and non-functional ones are easy to forget.

• 1Classify 5 sample requirements as functional or non-functional.
• 2Learn to specify non-functional requirements concretely (e.g. 'loads in under 2 seconds').
• 3Understand why skipping non-functional requirements causes expensive rework late in development.