diff --git a/framework-docs/modules/ROOT/pages/core/expressions/language-ref/variables.adoc b/framework-docs/modules/ROOT/pages/core/expressions/language-ref/variables.adoc
index 11874bd75f3..96d75477d83 100644
--- a/framework-docs/modules/ROOT/pages/core/expressions/language-ref/variables.adoc
+++ b/framework-docs/modules/ROOT/pages/core/expressions/language-ref/variables.adoc
@@ -6,11 +6,14 @@ are set by using the `setVariable()` method in `EvaluationContext` implementatio
 
 [NOTE]
 ====
-Valid variable names must be composed of one or more of the following supported
+Variable names must be begin with a letter (as defined below), an underscore, or a dollar
+sign.
+
+Variable names must be composed of one or more of the following supported types of
 characters.
 
-* letters: `A` to `Z` and `a` to `z`
-* digits: `0` to `9`
+* letter: any character for which `java.lang.Character.isLetter(char)` returns `true`
+* digit: `0` to `9`
 * underscore: `_`
 * dollar sign: `$`
 ====
diff --git a/spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java b/spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java
index 632cf4721b7..5ca7b3c30cc 100644
--- a/spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java
+++ b/spring-expression/src/main/java/org/springframework/expression/spel/standard/Tokenizer.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -93,8 +93,8 @@ class Tokenizer {
 							pushCharToken(TokenKind.PLUS);
 						}
 						break;
-					case '_': // the other way to start an identifier
-						lexIdentifier();
+					case '_':
+						lexIdentifier();  // '_' is another way to start an identifier
 						break;
 					case '-':
 						if (isTwoCharToken(TokenKind.DEC)) {
@@ -206,7 +206,7 @@ class Tokenizer {
 							pushPairToken(TokenKind.SELECT_LAST);
 						}
 						else {
-							lexIdentifier();
+							lexIdentifier();  // '$' is another way to start an identifier
 						}
 						break;
 					case '>':