The radical of an algebraic group is the identity component of its maximal normal solvable subgroup. For example, the radical of the general linear group (for a field K) is the subgroup consisting of scalar matrices, i.e. matrices with and for . An algebraic group is called semisimple if its radical is trivial, i.e., consists of the identity element only. The group is semi-simple, for example. The subgroup of unipotent elements in the radical is called the unipotent radical, it serves to define reductive groups. See also Reductive group Unipotent group References "Radical of a group", Encyclopaedia of Mathematics Algebraic groups