( ( The ( six ( known leptons ) ) ) ( ( are ( ( ( ( ( ( ( ( the electron ) , ) ( the muon ) ) , ) ( the ( tau lepton ) ) ) , ) and ) ( their ( respective neutrinos ) ) ) ) . ) )
(ROOT (S (NP (DT The) (CD six) (VBN known) (NNS leptons)) (VP (VBP are) (NP (NP (DT the) (NN electron)) (, ,) (NP (DT the) (NN muon)) (, ,) (NP (DT the) (NN tau) (NN lepton)) (, ,) (CC and) (NP (PRP$ their) (JJ respective) (NNS neutrinos)))) (. .)))
The six known leptons are the electron, the muon, the tau lepton, and their respective neutrinos.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD six) (NNS types)) (PP (IN of) (NP (NNS leptons))))) (. .)))