| ChemicalSubstance |
A chemical substance is 'a portion of matter of constant composition, composed of molecular entities of the same type or of different types' (source: [ChEBI:59999](https://www.ebi.ac.uk/chebi/searchId.do?chebiId=59999)). |
| Gene |
A discrete unit of inheritance which affects one or more biological traits (Source: [https://en.wikipedia.org/wiki/Gene](https://en.wikipedia.org/wiki/Gene)). Examples include FOXP2 (Forkhead box protein P2), SCARNA21 (small Cajal body-specific RNA 21), A- (agouti genotype). |
| MolecularEntity |
Any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer etc., identifiable as a separately distinguishable entity. |
| Protein |
Protein is here used in its widest possible definition, as classes of amino acid based molecules. Amyloid-beta Protein in human (UniProt P05067), eukaryota (e.g. an OrthoDB group) or even a single molecule that one can point to are all of type :Protein. A protein can thus be a subclass of another protein, e.g. :Protein as a UniProt record can have multiple isoforms inside it which would also be :Protein. They can be imagined, synthetic, hypothetical or naturally occurring. |