User models – the representation of user properties, preferences, goals, etc. – are crucial in modern educational applications. Several related processes, such as recommendations and user adaptations, depend on a user model. The increasing demand for new and more complex system features has resulted in an increasing complexity of user models. Ontologies are a tool to deal with this growing complexity. Well-defined and flexible ontologies can help developers cope with the inherent difficulties. In this paper, the authors present ARII-eL, an Ontology Network for Adaptive and Informal eLearning. ARII-eL defines a user model which is flexible, adaptable and scalable. ARII-eL has been developed for use in a range of educational settings including informal and interactive learning, for which there are not so many user models available for. In addition, we show the ARII-eL ontology network and user model and one application, practical case, and the user results. The massive use of social networks, wikis, collective repositories, instant messaging services, and other social applications is moving the learning process out of classrooms into informal environments, at least as a complement to the regular lessons; and learning applications should take advantage of this tendency. This work is a step forward in that direction.