Increasingly, biological and clinical scientists are using ontologies to serve integration and coordination of research across diverse organisms and scientific fields. Ontologies, in this context, are logically organized collections of terms defined in such a way that they can be used consistently across multiple disciplines to describe clinical and experimental data. Ontologies are used in aging research to unify experimental results from a broad range of fields including genetics, proteomics, (stem) cell biology, oncology, model organism biology, psychogerontology, and many more. We will explore against this background questions such as the following: What is aging? What is premature aging? And more specifically: Is aging a disease?