Abstract In the last decade, linguists have started to develop and make use of ontologies, encouraged by the progress made in areas such as Artificial Intelligence and the Semantic Web. This paper gives an overview of notions and dimensions of “ontology” and of ontologies for and in linguistics. It discusses building blocks, design aspects, and capabilities of formal ontologies and provides some implementation pointers. The focus of this paper, however, is on linguistic research and what a modelling framework based on ontologies has to offer. Accordingly, the paper does not aim at providing an overview of specific models for computational processing. To illustrate the issues at hand, an example scenario from linguistic typology is selected instead, where the aim of describing the world's languages is approached through ontologies.