To describe the Hund's coupling cases, we use the following angular momenta (where boldface letters indicate vector quantities):
*, the electronic orbital angular momentum
*, the electronic spin angular momentum
*, the total electronic angular momentum
*, the rotational angular momentum of the nuclei
*, the total angular momentum of the system (exclusive of nuclear spin)
*, the total angular momentum exclusive of electron (and nuclear) spin
These vector quantities depend on corresponding quantum numbers whose values are shown in molecular term symbols used to identify the states. For example, the term symbol Π denotes a state with S = 1/2, Λ = 1 and J = 3/2.