Symbols characterizing the states of atoms and molecules in terms of multiplicity, symmetry of the total electronic wavefunction, and sometimes total (orbital + spin) angular momentum. Examples: ${}^2{\mathrm{P}}_{1/2}$ denotes an atomic state of multiplicity 2 (doublet), electron orbital angular momentum quantum number $L=1$, and orbital plus spin angular momentum quantum number $J=\frac{1}{2}$.