EFO

EFO is an acronym used in several contexts, but one widely recognized meaning in the life sciences is the Experimental Factor Ontology. This ontology provides a controlled vocabulary for describing experimental variables and factors in biological research, with the aim of enabling consistent annotation and data integration across studies and databases.

The Experimental Factor Ontology (EFO) is designed to cover a broad range of terms, including diseases, phenotypes, cell types, assays, and other experimental factors. It assigns stable identifiers to concepts (for example, EFO_0000401) and establishes cross-references to related terms in other ontologies such as the Disease Ontology, MONDO, and Gene Ontology. The ontology is developed and maintained with collaboration from the European Bioinformatics Institute and aligns with the principles of the OBO Foundry to promote interoperability and reuse across resources.

EFO terms are used in major biomedical data resources and workflows to annotate experiments, samples, and study designs. They facilitate data integration, search, and comparative analyses across datasets generated by diverse platforms and studies. Notable applications include integration efforts in resources like GWAS Catalog, Expression Atlas, and related data repositories that rely on standardized experimental descriptors.

Other uses of the acronym exist in different domains, but there is no single alternate meaning with universal acceptance. This article focuses on the Experimental Factor Ontology as the principal widely adopted sense of EFO in scientific data management.