Systems Engineering is an interdisciplinary approach and means to enable the
realisation of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, then proceeding with design synthesis and system validation while considering the complete problem.
Systems Engineering integrates all the disciplines and specialty groups into a team effort forming a structured development process that proceeds from concept to production to operation. Systems Engineering considers both the business and the technical needs of all customers with the goal of providing a quality product that meets the user needs
(Reference Overview of the System Engineering Process, Ed Ryen, PE, North Dakota Department of Transportation)