We study the countable set of rates of growth of a hyperbolic group

with respect to all its finite generating sets. We prove that the set is

well-ordered, and that every real number can be the rate of growth of at most

finitely many generating sets up to automorphism of the group.

We prove that the ordinal of the set of rates of growth is at least

$\omega^\omega$, and in case the group is a limit group (e.g., free and surface groups), it is

$\omega^\omega$. This suggests a polynomial invariant of finite generating sets

of these limit groups.

We further study the rates of growth of all the finitely generated subgroups of

a hyperbolic group with respect to all their finite generating sets. This set

is proved to be well-ordered as well, and every real number can be the rate of

growth of at most finitely many isomorphism classes of finite generating sets

of subgroups of a given hyperbolic group. Finally, we strengthen our results to

include rates of growth of all the finite generating sets of all the

subsemigroups of a hyperbolic group.

Joint work with Koji Fujiwara.