This paper reports on the development of QoSOnt: an ontology for Quality of Service (QoS). Particular focus is given to its application in the field of service-centric systems. QoSOnt is being developed to promote consensus on QoS concepts, by providing a model which is generic enough for reuse across multiple domains. As well as the structure of the ontology itself, an example application currently in development, SQRM (Service QoS Requirements Matcher) is discussed. This application is used to highlight some of the advantages of the ontology. As well as standardisation, one such advantage is the ability to perform certain types of automated reasoning on QoSOnt and anything defined using QoSOnt.