Functional requirement is a specialized skill that involves defining the specific functions and features that a software system must have in order to meet the needs and expectations of its users. It requires an in-depth understanding of the users' requirements, workflow, and business processes. A functional requirement describes what the system is supposed to do and how it should behave, and it is typically expressed in a structured way using various tools and techniques. This skill is important in software development to ensure that the end product meets the desired business outcomes and provides a positive user experience.