This paper presents the developed domain ontology of the equipment in manufacturing systems in order to be used in the field of reconfigurable manufacturing systems (RMS). The ontology meets the requirements of the meta-class "Equipment", which is part of the developed meta ontology based on the standard for integrated systems for the production and management IEC / ISO 62264. The article explains various properties and class restrictions of the developed ontology. Web Ontology Language (OWL 2) and Protégé 4.3 as an editor and knowledge acquisition tool are used. Special attention is given to the use of ontology reasoning to infer additional information from the facts stated explicitly in ontology – an important feature, used to perform classification, sorting and assembly operations and consistency checking.