Lie algebra Lie subalgebra A Lie subalgebra 𝔥 is a subalgebra 𝔥 ≤𝔤 of a Lie algebra 𝔤, #m/def/lie i.e. it is closed under the Lie bracket, [𝔥,𝔥] ⊆𝔥. #state/tidy | #lang/en | #SemBr