  We formulate lattice fermions in a way that encompasses Wilson fermions as
well as the static and non-relativistic approximations. In particular, we treat
$m_qa$ systematically ($m_q$ is the fermion mass) showing how to understand the
Wilson action as an effective action for systems with $\vek{p}\ll m_q$. The
results show how to extract matrix elements and the spectrum from simulations
with $m_qa\approx1$, which is relevant for the charm quark.
