  In this paper, Grand Unified theories are discussed in terms of quaternions
and octonions by using the relation between quaternion basis elements with
Pauli matrices and Octonions with Gell Mann \lambda matrices. Connection
between the unitary groups of GUTs and the normed division algebra has been
established to re-describe the SU(5)gauge group. We have thus described the
SU(5)gauge group and its subgroup SU(3)_{C}\times SU(2)_{L}\times U(1) by using
quaternion and octonion basis elements. As such the connection between U(1)
gauge group and complex number, SU(2) gauge group and quaternions and SU(3) and
octonions is established. It is concluded that the division algebra approach to
the the theory of unification of fundamental interactions as the case of GUTs
leads to the consequences towards the new understanding of these theories which
incorporate the existence of magnetic monopole and dyon.

General Physics