In the study of special languages and translation, the legal field is often insulated from other domains. This is primarily due to the extreme system dependence of the terminology of law, which results from a lack of a common legal system of reference throughout the world. The abstract nature of this human-made field and its dynamicity in view of the continuously evolving case law and constant changes in legislation make it difficult to illustrate its complex ontology through traditional terminology management techniques. Therefore, this paper argues for an interdisciplinary approach to constructing the ontology of legal concepts based on structural constituents from frame semantics and comparative law. Frames allowing for the representation of interconnected knowledge segments evoked by legal concepts and the distinction between micro- and macro-dimensions in legal comparison research make it possible to capture the complex ontology of legal terminology evoked in a specific point in time and a determined legal context. The ontological knowledge structure will be exemplified by terms from German social, commercial, employment, and tax law.