Requirement (glossary)

Statement that identifies a product* or process operational, functional, or design characteristic or constraint, which is unambiguous, testable or measurable, and necessary for product or process acceptability. (ISO/IEC 2007) *includes product or service

Source

ISO/IEC. 2007. Systems and Software Engineering -- Recommended Practice for Architectural Description of Software-Intensive Systems. Geneva, Switzerland: International Organization for Standards (ISO)/International Electronical Commission (IEC), ISO/IEC 42010:2007.

Discussion

A requirement is “a statement that identifies a system, product or process characteristic or constraint, which is unambiguous, clear, unique, consistent, stand‐alone (not grouped), and verifiable, and is deemed necessary for stakeholder acceptability.” (INCOSE. 2010) p. 362.