  We prove curvature-free versions of the celebrated Margulis Lemma. We are
interested by both the algebraic aspects and the geometric ones, with however
an emphasis on the second and we aim at giving quantitative (computable)
estimates of some important invariants. Our goal is to get rid of the pointwise
curvature assumptions in order to extend the results to more general spaces
such as certain metric spaces. Essentially the upper bound on the curvature is
replaced by the assumption that the space is hyperbolic in the sense of Gromov
and the lower bound of the curvature by an upper bound on the entropy which we
recall the definition.
