diff --git a/src/model/glossary.ts b/src/model/glossary.ts
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+/**
+ * UI glossary (F11, G4) — one-line definitions of the language, surfaced where a
+ * newcomer meets each term: as palette tooltips before placing, and in the
+ * gloss-on-selection panel after.
+ *
+ * CONTEXT.md is the authority for the vocabulary; these are deliberately terser
+ * (a tooltip can't hold the full entry with its `Avoid:` clauses). Keep them in
+ * sync with CONTEXT.md by hand — there's no test runner yet to assert it; when
+ * one lands, a check that every `NodeKind` has an entry and each `term` matches a
+ * CONTEXT.md heading would close the drift gap.
+ */
+import type { NodeKind } from "./types"
+
+export interface GlossEntry {
+  /** The canonical term, verbatim from CONTEXT.md. */
+  term: string
+  /** A one-sentence gloss, distilled from the CONTEXT.md definition. */
+  short: string
+}
+
+export const NODE_GLOSSARY: Record<NodeKind, GlossEntry> = {
+  stock: {
+    term: "Stock",
+    short:
+      "An accumulation that holds a quantity over time — the system's memory. Only Flows can change it.",
+  },
+  flow: {
+    term: "Flow",
+    short:
+      "A rate that moves quantity into or out of a Stock — the only element that can change one.",
+  },
+  converter: {
+    term: "Converter",
+    short:
+      "A stateless helper value, recomputed each instant from its inputs (or a fixed constant).",
+  },
+  cloud: {
+    term: "Source / Sink",
+    short:
+      "The model boundary on an open Flow end — where quantity comes from (Source) or goes (Sink).",
+  },
+}
+
+export const INFO_LINK_GLOSS: GlossEntry = {
+  term: "Information Link",
+  short:
+    "Carries one element's value to a Flow or Converter — influence only, never quantity; its sign is its Polarity.",
+}