[Effectiveness, benefit and necessity: making an attempt at a scientific definition].

Effectiveness does not always mean benefit but there is no benefit without effectiveness. Benefit does not always involve necessity but there is no necessity without benefit. In spite of this simple relationship these three important terms of the social security regulations are not well-defined. The array of the terms "effectiveness", "benefit" and "necessity" exhibits a decreasing accuracy of definition, a diminishing popularity in the context of scientific discourse, a rising importance for cost compensation, an increase of context dependencies and growing judgement dependence.