With more than 4,000 research articles in 2022 the Circular Economy is clearly a topic that meets academic interest. With resource use at an all-time, unsustainable peak it is also a topic that raises great expectations: We need the circular economy. The great hopes that we all have are further fueled by the definitions of the circular economy that we find in the literature. Put colloquially, many of these definitions depict the circular economy as a “jack of all trades”. Some definitions include waste management while others are even synonymous with sustainable development. Attempts to summarize existing definitions into one result in definitions that blur the lines between the circular economy and other concepts even further. To empower the circular use of resources we need to understand what the circular economy really is and how it relates to related concepts. The role of definitions is to draw rather than blur lines. This is where many definitions fail. In our short article “Definitions of the Circular Economy: Circularity Matters”, we develop some conditions that good definitions must meet. By way of example, we apply these conditions to a popular definition that we found in the literature and we identify some of the shortcomings of existing definitions. We develop four conditions that we believe good definitions of the circular economy must meet. Good definitions of the circular economy must (1) refer to closing resource loops, (2) mention optimizing rather than minimizing resource flows, (3) consider at least two levels, and (4) distinguish between the circular economy as a perfect ideal type and a realistic imperfect circular economy that delivers sustainability in combination with other approaches. In this short paper, we propose a definition that meets all four conditions. We see the definition we propose neither as the start nor as the end of the discussion on how to define the circular economy. We see it as a mid-way point and as an invitation to researchers to join a discussion that we believe is necessary to leverage the potential that the circular economy can have for the sustainable development of all.