Engineering is an approach that involves a set of processes of applying knowledge and skills to understand and manage stakeholders’ requirements, propose and implement a solution to address those requirements, and utilize and support that solution to create value persistently until its retirement.
~ Wentz Wu

Systems Engineering

interdisciplinary approach governing the total technical and managerial effort required to transform a set of stakeholder needs, expectations, and constraints into a solution and to support that solution throughout its life.

Source: ISO/IEC/IEEE 15288:2015 Systems and software engineering — System life cycle processes

Software Engineering

application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.

Source: ISO/IEC/IEEE 12207:2017 Systems and software engineering — Software life cycle processes