ɪn mˌæθɪmˈæɾɪks, ɪspˈɛʃəli ɪn lˈaɪ θˈiəɹi, ˈɛn ɪz ðə kˈæk mˈuːdi ˈældʒᵻbɹə hˌuːz dˈɪŋkɪn dˈaɪəɡɹˌæm ɪz ɐ bˈaɪfɚkˌeɪɾɪŋ ɡɹˈæf wɪð θɹˈiː bɹˈæntʃᵻz ʌv lˈɛŋθ wˈʌn, tˈuː ænd kˈeɪ, wɪð kˈeɪ ˈiːkwəlz ˈɛn mˈaɪnəs fˈoːɹ.
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.