The I-ADOPT Framework is an ontology designed to facilitate interoperability between existing variable description models (including ontologies, taxonomy, and structured controlled vocabularies). One of the challenges in representing semantic descriptions of variables is getting people to agree about what they mean when describing the components that define the variables. The I-ADOPT ontology addresses this by providing core components and their relations that can be applied to define machine-interpretable variable descriptions that re-use FAIR vocabulary terms. This first version of the ontology has been developed by a core group of terminology experts and users from the Research Data Alliance (RDA) InteroperAble Descriptions of Observable Property Terminology (I-ADOPT) Working Group.