Requirements Specification

Definition: 

A detailed statement of the exact results wanted from a project or product.

The conditions or capabilities that must be met or possessed by a system, product in order to satisfy essential functionality, standards, solution to problem or other formally imposed documents. Requirements include the quantified and documented needs, wants and expectations of the inventor/customer.

A requirements specification details the desired end result of a project. This helps project managers to ensure that they are delivering exactly what their customers want, because their needs are specified and communicated clearly to those involved in the development of the project.