Scope of Work / Technical requirement Scope statement / Requirements Specification - requirements represent the application from the perspective of the user, or the business as a whole. Requirements document what is needed - they shouldn’t specify the how, but the what..
Functional Specification (Documents) - The specification represents the application from the perspective of the technical team. Specifications document how to achieve the requirements - they should specify the how. Explain design decisions and an implementation plan
Requirements are what the application DOES
Specifications are HOW the application does what it does.
Specifications and requirements roughly communicate the same information, but to two completely different audiences.
Determine the needs or conditions to meet for a new or altered product, taking account of the possibly conflicting requirements of the various stakeholders.
They provide a precise idea of the problem to be solved so that they can efficiently design the system and estimate the cost of design alternatives. They provide guidance to testers for verification (qualification) of each technical requirement.
The quote is from “Systems Engineering Fundamentals*”.
Requirements are based on stakeholders needs, specifications are more an inside detailed and technical document. They are different, but they talk about the same thing.By privilege15