Digitization is transforming previously physical products into holistic product-service systems which open up opportunities for new business models. But to achieve an excellent customer experience with them, a use case-specific configuration of the extensive product-service systems is necessary. One possible approach for the efficient implementation is to modularize the systems. In digital product-service systems, these modules require a holistic view that includes physical and digital resources as well as processes and people. The construct of capability might be a suitable framework to define such modules purpose-based and to manage the configuration. However, capabilities are not sufficiently defined in the literature and are, therefore, hardly ever used in practice. The aim of this paper is to create a common understanding of the term capability in the context of product-service systems with the help of an ontology.