The equation in the form originally proposed by Dirac is: {|cellpadding="6" style="border:2px solid #0073CF;background: #F5FFFA; text-align: center;" | |} where ψ = ψ(r, t) is a complex four-component field ψ that Dirac thought of as the wave function for the electron, r and t are the space and time coordinates, m is the rest mass of the electron, is the momentum operator, c is the speed of light, and ħ is the reduced Planck constant (h/2π). Furthermore, α is a vector operator whose components are 4 × 4 matricies: α = (α1, α2, α3), and β is another 4 × 4 matrix.