The MEG experiment in Switzerland measured violation of conservation of one type of this property. It’s not CP symmetry, but in particle interactions, special triangles defined in the complex plane bound the change in this property. Mechanisms that alter this general property called FCNCs are suppressed in the (15[1])Standard Model via the GIM mechanism. (15[1])This property is conserved in QCD but not by the weak force, and the PMNS matrix relates (*) neutrino mass eigenstates to (10[1])eigenstates of this quality. In beta decay, a proton becoming a neutron alters the baryon form of this attribute called isospin. The change between the electron, muon, and tau forms of this property are observed in neutrino oscillations. For 10 points, name this particle attribute that for quarks comes in six types and distinguishes top, down, and strange quarks. ■END■