Non-functional requirements, often abbreviated as NFRs, are an essential component of business analysis and software development. Unlike functional requirements, which specify what a system or product should do, non-functional requirements define how a system should perform and what qualities it should possess.

These requirements address aspects related to system behavior, performance, security, and user experience, among others.

Key aspects of non-Functional requirements:

1. Performance: Specifies system responsiveness, throughput, and scalability, including response times and load handling;
2. Reliability: Focuses on consistent performance, uptime metrics, error handling, fault tolerance, and disaster recovery;
3. Security: Addresses data protection, access control, encryption, and compliance with security standards;
4. Usability: Concerned with user-friendliness, accessibility, and user interface design;
5. Scalability: Defines adaptability to changing demands and growth without performance degradation;
6. Compliance: Ensures adherence to industry regulations, standards, and legal requirements;
7. Availability: Specifies expected uptime, downtime, and high availability mechanisms;
8. Interoperability: Deals with seamless integration with other systems or components;
9. Maintainability: Focuses on ease of system maintenance, including code readability and documentation;
10. Portability: Addresses the ability to run on different platforms or environments;
11. Performance Metrics: Includes specific performance metrics and acceptable thresholds for measurement;
12. Constraints: Describes limitations or restrictions, such as budget, technology, or regulatory constraints;
13. Trade-offs: Involves optimizing one aspect at the potential cost of another, requiring a balance.

Non-functional requirements are critical for ensuring that a system or product not only meets functional expectations but also delivers a positive user experience, performs reliably, and complies with relevant standards and regulations.