diff --git a/docs/grammar.ebnf b/docs/grammar.ebnf
index de02951..aa033f6 100644
--- a/docs/grammar.ebnf
+++ b/docs/grammar.ebnf
@@ -738,9 +738,18 @@ QualIdent
 ArrayType
     = ARRAY LBRACKET ArrayBound DOTDOT ArrayBound
             { COMMA ArrayBound DOTDOT ArrayBound } RBRACKET OF TypeName
-    | ARRAY LBRACKET IDENT RBRACKET OF TypeName   (* ordinal/enum-indexed *)
+    | ARRAY LBRACKET IDENT RBRACKET OF TypeName   (* ordinal-indexed *)
     ;
 
+(* The IDENT form names an ORDINAL index type.  Two ordinal kinds are admitted:
+ *   - an enumeration type (array[TColor] of T folds to array[0..N-1] of T,
+ *     where N is the member count), and
+ *   - a NAMED integer subrange (type TIdx = lo..hi;  array[TIdx] of T folds to
+ *     array[lo..hi] of T).  The subrange supplies only the index range; the
+ *     values it yields remain ordinary unchecked integers of the subrange's
+ *     underlying storage type.
+ * See language-rationale.adoc "Array index types". *)
+
 ArrayBound
     = ConstArithExpr
     ;
diff --git a/docs/language-rationale.adoc b/docs/language-rationale.adoc
index 2e5dcf2..f8be8db 100644
--- a/docs/language-rationale.adoc
+++ b/docs/language-rationale.adoc
@@ -1154,6 +1154,9 @@ Blaise supports fixed-size, stack-allocated arrays declared as
 | `array[TEnum] of T` — enum-type index
 | Supported
 
+| `array[TSubrange] of T` — named integer-subrange index
+| Supported. The subrange (`type TIdx = lo..hi;`) supplies the index range, so `array[TIdx] of T` folds to `array[lo..hi] of T`; the subrange's values remain ordinary unchecked integers of its underlying storage type.
+
 | `array[L..H, M..N] of T` — multi-dimensional
 | Supported