  We provide scaling relations and fitting formulae for adiabatic cold dark
matter cosmologies that account for all baryon effects in the matter transfer
function to better than 10% in the large-scale structure regime. They are based
upon a physically well-motivated separation of the effects of acoustic
oscillations, Compton drag, velocity overshoot, baryon infall, adiabatic
damping, Silk damping, and cold-dark-matter growth suppression. We also find a
simpler, more accurate, and better motivated form for the zero baryon transfer
function than previous works. These descriptions are employed to quantify the
amplitude and location of baryonic features in linear theory. While baryonic
oscillations are prominent if the baryon fraction exceeds $\Omega_0 h^2 + 0.2$,
the main effect in more conventional cosmologies is a sharp suppression in the
transfer function below the sound horizon. We provide a simple but accurate
description of this effect and stress that it is not well approximated by a
change in the shape parameter $\Gamma$.
