Molecular entity

According to the IUPAC Gold Book a molecular entity is "any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable entity".

Molecular entity is used as a general term for any singular entity, irrespective of its nature, in order to concisely express any type of chemical particle that can exemplify some process: for example, atoms, molecules, ions, etc. can all undergo a chemical reaction.