  I present an overview of the calculations of the isovector axial vector form
factor of the nucleon, $G_A(Q^2)$, using lattice QCD. Based on a comparison of
results from various collaborations, a case is made that lattice results are
now consistent within 10\%. A similar level of uncertainty is found also in the
axial charge $g_A^{u-d}$, the mean squared axial charge radius, $\langle r_A^2
\rangle$, the induced pseudoscalar charge $g_P^\ast$, and the pion-nucleon
coupling $g_{\pi NN}$. These lattice results for $G_A(Q^2)$ are already
compatible with those obtained from the recent MINER$\nu$A experiment but lie
2-3$\sigma$ higher than the phenomenological extraction from the old
$\nu$-deuterium bubble chamber scattering data for $Q^2 > 0.3$~GeV${}^2$. Fits
to our data show that the dipole ansatz does not have enough parameters to
parameterize the form factor over the range $0 \le Q^2 \le 1$~GeV${}^2$,
whereas even a $z^2$ truncation of the $z$-expansion or a low order Pad\'e are
sufficient. Looking ahead, lattice QCD calculations will provide increasingly
precise results over the range $0 \le Q^2 \lesssim 1$~GeV${}^2$, and
MINER$\nu$A-like experiments will extend the range to $Q^2 \sim 2$~GeV${}^2$ or
higher. To increase precision of lattice data to the percent level, new
developments are needed to address two related issues: the exponentially
falling signal-to-noise ratio in all nucleon correlation functions and removing
excited state contributions. Nevertheless, even with the current methodology,
significant reduction in errors is expected over the next few years with higher
statistics data on more ensembles closer to the physical point.
