In mathematics, a split-biquaternion is a hypercomplex number of the form q = w + x i + y j + z k, {\displaystyle q=w+x\mathrm {i} +y\mathrm {j} +z\mathrm {k},} where w, x, y, and z are split-complex numbers and i, j, and k multiply as in the quaternion group. Wikipedia