Marked length spectrum
= Marked length spectrum
{title2=$[\gamma]\mapsto\ell(\gamma)$}
For a closed <hyperbolic surface> with a specified marking of its <fundamental group>, assign to each nontrivial conjugacy class the length of its unique closed <geodesic>. Retaining the group label is stronger than retaining only the unmarked length multiset: it also records which lengths belong to intersecting curves or powers of particular curves.