En (Lie Algebra)
In mathematics, especially in Lie theory, En is the Kac–Moody algebra whose Dynkin diagram is a bifurcating graph with three branches of length 1,2, and k, with k=n-4.
In some older books and papers, E2 and E4 are used as names for G2 and F4.
Read more about En (Lie Algebra): Finite Dimensional Lie Algebras, Infinite Dimensional Lie Algebras, Root Lattice, E7½