ChEBI (meaning "Chemical Entities of Biological Interest", or "Chemistry at the EBI") is a database of molecular entities focused on 'small' chemical compounds. The term "molecular entity" refers to any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity . The molecular entities in question are either products of nature or synthetic products used to intervene in the processes of living organisms. Molecules directly encoded by the genome, such as nucleic acids, proteins and peptides derived from proteins by proteolytic cleavage, are not as a rule included in ChEBI.
ChEBI includes an ontological classification, whereby the relationships between molecular entities or classes of entities and their parents and/or children are specified.
ChEBI uses nomenclature, symbolism and terminology endorsed by the International Union of Pure and Applied Chemistry (IUPAC) and Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB).