This study presents a core ontology for missions and capabilities in systems of systems. The aim of the study is to create artifacts that facilitate precise understanding of fundamental concepts of SoS. An ontological approach proposes and develops taxonomic homogeneity and structural knowledge of SoS. The ontology development process involved workshop sessions with industry experts and meta modelling of the different concepts and their relationships. The ontology includes thirteen concepts of types physical things, people, information and mixed. These concepts are defined and their relations are briefly described. The developed ontology is further illustrated using a wildfire scenario case study.