Thirdly, the Landé g-factor, g J, is defined by | μ μ J | = g J μ μ B ℏ ℏ | J | where μ J is the total magnetic moment resulting from both spin and orbital angular momentum of an electron, J = L + S is its total angular momentum, and μ B is the Bohr magneton. The value of g J is related to g L and g s by a quantum-mechanical argument; see the article Landé g -factor. μ J and J vectors are not collinear, so only their magnitudes can be compared.