Non-Functional Requirements: It refers to needs that must be fulfilled related to things. They do not deal with the actual functionality of the system but represents key project success factors nevertheless. List of Non-functional requirements are
user interface,
access security,
Availability,
Robustness,
System Failure,
Integration,
Migration,
Documentation,
Installability,
Maintainability,
Portability,
Reliability,
Scalability,
Multiple Environment Support,
Extensibility,
Reuse,
Operability,
Privacy,
Security.