differentiable manifold

noun2

1. •
   A manifold that is locally similar enough to a Euclidean space (ℝⁿ) to allow one to do calculus;

   • The charts (homeomorphisms) that make up any differentiable structure of a differentiable manifold are required to be such that the transition from one to another is differentiable.
2. •
   a manifold that can be equipped with a differentiable structure (an atlas of ℝⁿ-compatible charts).