  Let $\Lambda$ be a lattice in $\R^n$, and let $Z\subseteq \R^{m+n}$ be a
definable family in an o-minimal structure over $\R$. We give sharp estimates
for the number of lattice points in the fibers $Z_T={x\in \R^n: (T,x)\in Z}$.
Along the way we show that for any subspace $\Sigma\subseteq\R^n$ of dimension
$j>0$ the $j$-volume of the orthogonal projection of $Z_T$ to $\Sigma$ is, up
to a constant depending only on the family $Z$, bounded by the maximal
$j$-dimensional volume of the orthogonal projections to the $j$-dimensional
coordinate subspaces.
