definition. Spin group [li2008invariant] [spin-0004]

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A versor refers to a Clifford monomial composed of invertible vectors. It is called a rotor, or spinor, if the number of vectors is even. It is called a unit versor if its magnitude is 1.

All versors in \(\mathcal {C L}\left (\mathcal {V}^n\right )\) form a group under the geometric product, called the versor group, also known as the Clifford group, or Lipschitz group. All rotors form a subgroup, called the rotor group. All unit versors form a subgroup, called the pin group, and all unit rotors form a subgroup, called the spin group, denoted by \(\operatorname {Spin}\left (\mathcal {V}^n\right )\).