Foundation Lemma: Constitutional Principles and Nomenclature This document establishes the foundational terminology, constitutional principles, and conceptual scope of the Signature Framework. The work does not propose new particles, forces, or modifications to established physical laws. Instead, it introduces a common language for describing interaction, carrier-mediated processes, reaction surfaces, carrier loading, and related structural concepts employed throughout subsequent framework developments. Particular emphasis is placed on process continuity, interaction primacy, finite coupling, observation as energetic interaction, and the distinction between localized configurations and distributed process-load domains. The document is intended as a constitutional reference and nomenclature framework rather than as a standalone predictive physical theory. Its primary purpose is to provide conceptual consistency and terminological clarity across later works, including developments involving reaction surfaces, carrier loading, OSPLD (Omnidirectional Spherical Process-Load Domains), constitutive gravity, inertial response, and related interaction-based interpretations.