 Exceptional Lie algebras

Exceptional Lie algebras are a special class of Lie algebras that are neither classical nor affine. They are characterized by their exceptional properties, most notably their dimension and the structure of their root systems. Unlike the classical Lie algebras (which include types A, B, C, D corresponding to the classical groups, and E, F, G corresponding to exceptional types), the exceptional Lie algebras cannot be directly described in terms of standard matrix groups.