Hyperelasticity is intended to represent a class of elastomeric materials that consist of long chain molecular structures. On a macroscopic level, the initial stiffness slope typically is representative of untangling these long chain of molecules. The increase in stiffness with increased strain is typically representative of stretching the molecular chains after they become untangled. These materials have memory. So once the load is removed, the material returns to its original shape (no residual strain is observed).