system

This term is defined in ECSS-E-ST-35C Rev. 1 as
See propulsion system (see 3.2.1.54).

This term is defined in ECSS-Q-ST-40C as
set of interdependent elements constituted to achieve a given objective by performing a specified function [IEC 50:1992]

This term is defined in ECSS-S-ST-00-01C as
set of interrelated or interacting functions constituted to achieve a specified objective