The market is expounded by different scientific disciplines, judged by different normative positions, and experienced by different actors. Despite this omnipresence, there is no discernible consensus that answers the question what a market is per se. In contention with theoretical arguments about the market and with the help of systems theory, the article seeks to develop a robust notion of the market. Market can thus be understood as the internal environment of the economic system. Market happens, if both the communication of exchange and the observation of competitors blend into each other, and if these processes focus on and crystallize in prices.