Definitions

System
An interacting combination of elements to accomplish a defined objective. These include hardware, software, firmware, people, information, techniques, facilities, services, and Other support elements.

Systems Engineering
An interdisciplinary approach and means to enable the realization of successful systems.

Systems Engineer
An engineer trained and experienced in the field of systems engineering.

Systems Engineering Processes
A logical, systematic set of process steps selectively used to accomplish systems engineering tasks.

Product Creation/Generation Process (PCP/PGP)
A logical, systematic set of process steps to create/generate a product or system.

System Architecture
The arrangement of elements and subsystems and the allocation of
functions to them to meet the system requirements.

System Design
The activity where it is determined how the system will be realized

Requirements
The list of functionalities that the customer would like to have in the system.

Specification
The list of unambiguously measurable functionalities that are planned to be
realized in the system.

Performance
The list of unambiguously measurable functionalities that are realized after
completion of the system.

Property
The list of both wanted and unwanted both unambiguously measurable and
not well measurable functionalities of a system.

What is the difference CE vs MSD

Control theory:

Goal: select a suitable $u(t)$ such that a given system behaves the way you want it to (often based on optimization).

Mechatronic system design:

The system designer has significant control over $x,u,$ and the system structure $f$. Because of the vast number of design freedoms, it is almost impossible to develop a fully optimal system since it is very difficult to define a clear optimization criterion.

The V-Model of System Engineering