diff --git a/src/words.test.ts b/src/words.test.ts
index 13488ff..729e039 100644
--- a/src/words.test.ts
+++ b/src/words.test.ts
@@ -53,4 +53,15 @@ describe("Text Words", () => {
   ])("Concat(%s, %s)", (left, right, expected) =>
     expect(Concat(left, right)).toEqual(expected)
   );
+
+  test.each([
+    [null, { bare: "1", pos: 13 }, { text: "1", pos: 13 }],
+    [null, { text: "2", pos: 13 }, { text: "2", pos: 13 }],
+    [null, { html: "3", pos: 13 }, { html: "3", pos: 13 }],
+    [{ bare: "4", pos: 13 }, { bare: "5", pos: 15 }, { text: "45" }],
+    [{ html: "6", pos: 13 }, { html: "7", pos: 15 }, { html: "67" }],
+  ])(
+    "Concat(%s, %s) strips source position when combining words",
+    (left, right, expected) => expect(Concat(left, right)).toEqual(expected)
+  );
 });
diff --git a/src/words.ts b/src/words.ts
index c46e79f..c4884c8 100644
--- a/src/words.ts
+++ b/src/words.ts
@@ -1,4 +1,6 @@
-import { escapeHtml } from "./helpers";
+import { escapeHtml } from './helpers';
+
+export type SourcePos = number;
 
 /**
  * A word whose value is text with provenance- this literal value appeared in the source code,
@@ -15,13 +17,15 @@ import { escapeHtml } from "./helpers";
  */
 export type BareWord = {
   bare: string;
+  pos?: SourcePos;
 };
 
 /**
- * A word whose value is plain text, with no special provenance.
+ * A word whose value is plain text
  */
 export type TextWord = {
   text: string;
+  pos?: SourcePos;
 };
 
 /**
@@ -78,9 +82,12 @@ export function AsHtml(word: TextPiece | ErrorResult): string {
 }
 
 // safely concatenate text pieces, converting as needed
-export function Concat(left: TextPiece | null, right: TextPiece) {
+export function Concat(
+  left: TextPiece | null,
+  right: TextPiece
+): TextWord | HtmlWord {
   if (left === null) {
-    return "bare" in right ? { text: right.bare } : right;
+    return "bare" in right ? { text: right.bare, pos: right.pos } : right;
   }
   if ("html" in left || "html" in right) {
     return { html: AsHtml(left) + AsHtml(right) };