In the creation of a new nomenclature for economic systems theory, Nicklas Luhmann's sociological conceptualism may sometimes perform a heuristic role. In particular, the concepts of 'autopoiesis system' and 'observation of observations' can be extremely useful for the analysis of a far-reaching constellation of various economic concepts. This study develops the elementary terminology of metaeconomics and economic systems theory, and emphasizes the significance of the 'observation of observations'. In most cases when several fundamental concepts need to be logically constructed, the corresponding mathematical symbols and notions may often be utilized as the means for representing their formal functions. Amongst others, 'category' is the most important, because it can formalize the structure of economic systems and meta-observations from the viewpoint of logical foundations.