This thesis discusses two key topics: strangeness and charge symmetry violation (CSV) in the
nucleon. It also provides a pedagogical introduction to chiral effective field theory tailored
to the high-precision era of lattice quantum chromodynamics (QCD). Because the nucleon has zero
net strangeness strange observables give tremendous insight into the nature of the vacuum
they can only arise through quantum fluctuations in which strange-antistrange quark pairs are
generated. As a result the precise values of these quantities within QCD are important in
physics arenas as diverse as precision tests of QCD searches for physics beyond the Standard
Model and the interpretation of dark matter direct-detection experiments. Similarly the
precise knowledge of CSV observables has with increasing experimental precision become
essential to the interpretation of many searches for physics beyond the Standard Model. In this
thesis the numerical lattice gauge theory approach to QCD is combined with the chiral
perturbation theory formalism to determine strange and CSV quantities in a diverse range of
observables including the octet baryon masses sigma terms electromagnetic form factors and
parton distribution functions. This thesis builds a comprehensive and coherent picture of the
current status of understanding of strangeness and charge symmetry violation in the nucleon.
