Requirements are the Core unit of work for Business Analysts.

The IIBA state that a requirement is;

1. A condition or capability needed by a stakeholder to solve a problem or achieve an objective.
2. A condition or capability that must be met or possessed by a solution or solution component to satisfy a contract, standard, specification, or other formally imposed documents.
3. A documented representation of a condition or capability as in (1) or (2). ¹

The IIBA sets out a standard schema which is used to define and categorise requirements. The taxonomy they use is;

• Business Requirement
• Stakeholder Requirement
• Solution Requirement
• Transition Requirement

They further break down solution requirements into functional and non-functional, term which business analyst will hear often.

Requirements as a single unit of work can be prioritised, organised, modelled and constrained. Requirements have a life cycle and need management throughout the project.

The most important concept for understanding and working with Requirements is verification and validation.