Chirality for a Dirac fermion ψ is defined through the operator γ, which has eigenvalues ±1; the eigenvalue's sign is equal to the particle's chirality: +1 for right-handed, −1 for left-handed. Any Dirac field can thus be projected into its left- or right-handed component by acting with the projection operators ⁠ 1 / 2 ⁠ (1 − γ) or ⁠ 1 / 2 ⁠ (1 + γ) on ψ.