This study advances the Law of the Trio as a universal law of linguistics, positing that reality, thought, and language are ontologically equivalent yet formally distinct modalities of existence. Unlike prior frameworks that isolate language as computation, code, or communicative tool, the Trio establishes a foundational architecture: the recursive coupling of entity and state/behavior, enriched by layered modifiers. Sentences are reframed as semantic DNA, encoding identity, transformation, and relational depth across modalities. To formalize this claim, the paper introduces EMi/VMi,j notation, where i indexes modifier type and j denotes recursion depth. Worked examples and cross‑linguistic analysis (English, Korean, Basque) confirm semantic invariance across typologically distinct languages. Direct mapping to event semantics and thematic roles highlights both alignment and innovation, with recursion depth providing a computable dimension absent from existing models. Comparative analysis shows how the Trio consolidates and extends generative grammar, cognitive science, pedagogy, and semiotics by resolving their limitations through recursive semantic geometry. Applications in pedagogy and natural language processing demonstrate practical relevance. By restructuring linguistics into semantic geometry, the Trio offers a testable, falsifiable, and universal law of language that unifies theory and practice.