In differential geometry, a hyperkähler manifold is a Riemannian manifold {\displaystyle } endowed with three integrable almost complex structures I, J, K {\displaystyle I,J,K} that are Kähler with respect to the Riemannian metric g {\displaystyle g} and satisfy the quaternionic relations I 2 = J 2 = K 2 = I J K = − 1 {\displaystyle I^{2}=J^{2}=K^{2}=IJK=-1}. Wikipedia