In this monograph a fundamental distinction is made between law and juridical thinking. Law is the content of legal rules and the systems of legal rules. Juridical thinking is the handling of the law by the lawyers. To this distinction corresponds a basic distinction between the language of law and the language of juridical thinking, and correlatively, between L-concepts (law concepts) and J-concepts (juridical or jurisprudential concepts). The monograph is devoted to the J-concepts, especially of technical (not ideological or evaluative) J-concepts. Four kinds of J-concepts are investigated: morphological J-concepts, those that help us to structure the law in a logical and functional way; topological J-concepts,