What we want to do here is clarify a number or important concepts that are sometimes used as equivalents in environmental sciences and practices, but that might require some distinctions and specifications. We specify concepts like multidisciplinarity, interdisciplinarity, transdisciplinarity, but also disciplinarity and pluridisciplinarity. Maybe if we had a more clear conscience of those issues, we would understand each other along the way in collaborative projects. We also show how they shed light on specific issues, for instance water governance issues, and we distinguish these problems from valid questions of interprofessionality.