Features of a FAIR vocabulary

Abstract Background: The FAIR Principles explicitly require the use of FAIR vocabularies, but what precisely constitutes a FAIR vocabulary remains unclear. Being able todefine FAIR vocabularies, identify features of FAIR vocabularies, and provide assessment approaches against the features can guide the development of vocabularies.Results: We differentiate data, data resources and vocabularies used for FAIR, examine the application of the FAIR Principles to vocabularies, align their requirements with the Open Biomedical Ontologies (OBO) Principles, and propose FAIR Vocabulary Features (FVFs). We also design assessment approaches for FAIR vocabularies by mapping the FVFs with existing FAIR assessment indicators. Finally, we demonstrate how FVFs can be used for evaluating and improving vocabularies using exemplar biomedical vocabularies.Conclusions: The FAIR Vocabulary Features and corresponding indicators can be used to assess the FAIR levels of different types of vocabularies, identify use cases for vocabulary engineers, and guide the evolution of vocabularies.