The aim of this paper is to offer a conceptual analysis of the notion of failure of engineering artifacts focusing on aspects that are of import for a possible ontological formalization. Failure is a central notion in engineering, yet different taxonomies exist in the various industries and engineering domains that are not mutually compatible thereby hindering knowledge exchange. A formal definition of failure would contribute to improve knowledge exchange. However, in order to be successful such formalization should rest on shared conceptualizations. The paper analyses how the notion of failure is used in engineering, starting with the so-called “traditional definition”. Then, it is shown that engineers are willing to consider as failures also events and circumstances that are at odds with this traditional definition. Therefore, it is argued that, in order to capture adequately engineering conceptualizations, three independent notions of failure should be distinguished, which are called function-based failure, specification-based failure, and material-based failure.