"Criminal justice is the system of practices and institutions of governments directed at upholding social control, deterring and mitigating crime, or sanctioning those who violate laws with criminal penalties and rehabilitation efforts. Those accused of crime have some protections against abuse of investigatory and prosecution powers." ~ Wikipedia

So there's the usual sort of uninspired definition of a "system." It is a pretty good definition in the sense that it covers most of the areas of interest to those committed to conventional thinking. Howevever, let's take the same stuff and extract it from the box of conventional academia and career-ology. The range of passions for lifelong learning and opportunities for doing hands-on work--in your own time and in your own way--has few parallels.