  Despite stringent constraints set by astrophysical observations, there remain
viable scalar-tensor theories that could be distinguished from general
relativity with gravitational-wave detectors. A promising signal predicted in
these alternative theories is dynamical scalarization, which can dramatically
affect the evolution of neutron-star binaries near merger. Motivated by the
successful treatment of spontaneous scalarization, we develop a formalism that
partially resums the post-Newtonian expansion to capture dynamical
scalarization in a mathematically consistent manner. We calculate the
post-Newtonian order corrections to the equations of motion and scalar mass of
a binary system. Through comparison with quasi-equilibrium configuration
calculations, we verify that this new approximation scheme can accurately
predict the onset and magnitude of dynamical scalarization.
