The #dalton (symbol: Da), or #unifiedAtomicMassUnit (symbol: u), is a unit of mass defined as 1/12 of the mass of an #unbound neutral atom of #carbon12 in its nuclear and electronic #groundState and #atRest. It is a #nonSIUnitAcceptedForUseWithSI. The word "unified" emphasizes that the definition was accepted by both #IUPAP and #IUPAC. The #atomicMassConstant, denoted mu, is an atomic-scale reference mass, defined identically, but it is not a unit of mass.



