This paper develops a structural distinction between content-velocity and metric-velocity within relativistic physics. Content-velocity describes the motion of particles, field excitations, and information-bearing signals through spacetime, and is bounded by the local causal structure defined by ccc. Metric-velocity describes structural evolution of the spacetime metric itself—changes in geometric relations among events or comoving separations—and is not equivalent to localized signal propagation. A substrate-motion operator is introduced to formalize admissible metric reconfigurations, together with continuity, bounded-deformation, and causal-preservation conditions. The framework further provides a classification of wave-like phenomena into content waves, metric waves, and non-signal structural modes. The analysis is conceptual and classificatory in scope. It introduces no new dynamics, does not modify general relativity, and does not permit faster-than-light information transfer. Instead, it isolates and formalizes a distinction implicit in relativistic physics. The purpose of the work is to clarify why superluminal coordinate or cosmological recession behavior—familiar from FLRW cosmology—remains compatible with local relativistic causality when properly distinguished from content-motion. The framework provides a consistent structural vocabulary for discussing metric evolution without conflating it with signal propagation.
William T. Partin (Sun,) studied this question.