What is the difference between a Functional Requirement and a System Requirement?

As I know, the term 'Functional requirement' refers to a requirement which describes a function that needs to be implemented to solve a problem.

But what is meant by the term 'System requirement' and how does that relate to 'Functional requirement'?

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    I have taken the liberty to edit your question to what I think you meant to ask (about the terms, not the documents of the linked question). If this is not what you intended, feel free to roll the edit back. Commented Nov 5, 2014 at 14:05
  • A system requirement is a specification for a system... equipment, software, whatever. When you purchase s piece of software, it comes with "system requirements..." the minimum hardware specifications that it will run on. See en.wikipedia.org/wiki/System_requirements Commented Nov 5, 2014 at 15:13

1 Answer 1


In the context of requirements engineering, the concept of a "system requirement" is referring to a level of decomposition. In a sufficiently complex system, you could have any number of components (where a component could be hardware or software elements). Each component would have its own requirements, usually derived from the system requirements, that can be used to verify the behavior of the component in isolation prior to integration and verification and validation of the system as a whole throughout the integration process.

In the comments, Robert Harvey mentions another type of "system requirements": the required characteristics of the system that the software is being deployed on. These often include the hardware, operating system, and maybe even software dependencies. These would often be based on the technical system requirements that I mentioned above.

A functional requirement is a definition of a result of the system. The set of functional requirements on a system or component define what the system does. The opposite of a functional requirement is a non-functional requirement, which define attributes of a system, such as reliability, fault tolerance, documentation, security, testability, etc.

System requirements can be functional or non-functional, and define the behavior and attributes of a set of components.

  • Some brief examples would go a long way here. Commented Nov 5, 2014 at 16:39
  • Thanks for the explanation. It will be great if you can provide example for system requirement and functional requirement. Commented Nov 6, 2014 at 9:37

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