The article discusses the application of non-abelian discrete groups to the theory of neutrino masses and mixing, particularly focusing on the Tri-Bimaximal (TB) mixing pattern. It reviews the motivation and formalism behind using discrete flavor symmetries, and discusses specific models based on groups like A₄, S₄, and others. These models are analyzed for their phenomenological implications, including lepton flavor violation, leptogenesis, and extensions to quarks. The article also considers the application of discrete flavor symmetries to quark-lepton complementarity and Bimaximal Mixing (BM). The article begins by summarizing the results of neutrino oscillation experiments, which have established that neutrinos have mass and provided information about mixing angles and mass differences. It discusses the implications of these results, including the possibility of lepton number violation and the Majorana nature of neutrinos. The article also addresses the challenges in determining the absolute neutrino mass scale and the Dirac/Majorana nature of neutrinos. The article then explores the role of discrete flavor symmetries in neutrino mixing, particularly the A₄ group, which is shown to be a natural candidate for reproducing the TB mixing pattern. It discusses the structure of the A₄ group, its representations, and how it can be used to generate the TB mixing matrix. The article also considers other groups like S₄ and Δ(27) and their applications in neutrino mixing models. The article discusses the implications of the TB mixing pattern for neutrino mass hierarchies and the possibility of lepton flavor violation. It also addresses the role of discrete flavor symmetries in explaining the observed neutrino mixing angles and the potential for quark-lepton complementarity. The article concludes by emphasizing the importance of discrete flavor symmetries in understanding the flavor problem in particle physics and their potential to provide insights into the underlying structure of the Standard Model and beyond.The article discusses the application of non-abelian discrete groups to the theory of neutrino masses and mixing, particularly focusing on the Tri-Bimaximal (TB) mixing pattern. It reviews the motivation and formalism behind using discrete flavor symmetries, and discusses specific models based on groups like A₄, S₄, and others. These models are analyzed for their phenomenological implications, including lepton flavor violation, leptogenesis, and extensions to quarks. The article also considers the application of discrete flavor symmetries to quark-lepton complementarity and Bimaximal Mixing (BM). The article begins by summarizing the results of neutrino oscillation experiments, which have established that neutrinos have mass and provided information about mixing angles and mass differences. It discusses the implications of these results, including the possibility of lepton number violation and the Majorana nature of neutrinos. The article also addresses the challenges in determining the absolute neutrino mass scale and the Dirac/Majorana nature of neutrinos. The article then explores the role of discrete flavor symmetries in neutrino mixing, particularly the A₄ group, which is shown to be a natural candidate for reproducing the TB mixing pattern. It discusses the structure of the A₄ group, its representations, and how it can be used to generate the TB mixing matrix. The article also considers other groups like S₄ and Δ(27) and their applications in neutrino mixing models. The article discusses the implications of the TB mixing pattern for neutrino mass hierarchies and the possibility of lepton flavor violation. It also addresses the role of discrete flavor symmetries in explaining the observed neutrino mixing angles and the potential for quark-lepton complementarity. The article concludes by emphasizing the importance of discrete flavor symmetries in understanding the flavor problem in particle physics and their potential to provide insights into the underlying structure of the Standard Model and beyond.