[gregshue]

Add most broad NIST definition of "requirement" still suitable for system engineering.

[gregshue]

Here is a more-restrictive definition to consider as an alternative:

condition or capability that is met or possessed by a system, system component, product, or service to satisfy an agreement, standard, specification, or other formally imposed documents (IEEE 730-2014 IEEE Standard for Software Quality Assurance Processes, 3.2)

[gregshue]

Here are the Notes for the 'requirement' entry in 29148:2018 that were removed for 29148:2023 -

Note 1 to entry: Requirements exist at different levels in the system structure.
Note 2 to entry: A requirement is an expression of one or more particular needs in a very specific, precise and unambiguous manner.
Note 3 to entry: A requirement always relates to a system, software or service, or other item of interest.