In mathematics, an element x of a Lie group or a Lie algebra is called an n-Engel element, named after Friedrich Engel, if it satisfies the n-Engel condition that the repeated commutator [...[[x,y],y], ..., y] with n copies of y is trivial. It is called an Engel element if it satisfies the Engel condition that it is n-Engel for some n.