  Currently running and forthcoming precision neutrino oscillation experiments
aim to unambiguously determine the neutrino mass ordering, the charge-parity
violating phase in the lepton sector and the possible existence of physics
Beyond the Standard Model. To have an understanding of all the effects
necessary for the success of these experiments, lepton-nucleus interactions
must be modeled in unprecedented detail. With this thesis, expertise in both
neutrino and electron cross-section modeling and analysis was leveraged in
order to make fundamental and critical improvements to our understanding of
these interactions. The outlined work takes a significant step towards this
high-precision measurement era with three complementary approaches. Cross
sections are reported using neutrino data sets from the MicroBooNE liquid argon
time projection chamber detector at Fermi National Laboratory, as well as
electron scattering data from the CLAS detector at Thomas Jefferson National
Laboratory. Furthermore, the modeling development of the commonly used GENIE
event generator is presented.
