Deformable objects are physical entities whose shape, volume, or geometric configuration can change when subjected to external forces or manipulation. Unlike rigid bodies, in which the relative distances between all internal points remain fixed during motion, deformable objects undergo transformations such as bending, stretching, twisting, or compression. These objects encompass a diverse range of materials, including linear entities like ropes and cables, planar materials like cloth and paper, and volumetric or viscous items like foam, soft tissues, and dough. Because their configurations cannot be described solely by standard rigid-body poses, deformable objects are characterized by high-dimensional or infinite degrees of freedom, complex internal dynamics, and non-linear responses to contact and force.