diff --git a/docs/api/query-clauses.md b/docs/api/query-clauses.md
index d08b336..8d594cd 100644
--- a/docs/api/query-clauses.md
+++ b/docs/api/query-clauses.md
@@ -294,6 +294,31 @@ FOR user IN users
 
 [ArangoDB AGGREGATE documentation](https://www.arangodb.com/docs/stable/aql/operations-collect.html#aggregation)
 
+## WINDOW
+```
+window(
+        array|object $offsets,
+        string|QueryBuilder|Expression $rangeValue = null
+    )
+```
+Aggregate adjacent documents or value ranges with a sliding window
+to calculate running totals, rolling averages, and other statistical properties
+
+**Example 1:**
+```php
+$qb->window(['preceding' => 5, 'following' => 10])
+``` 
+Resulting AQL: `... WINDOW { "preceding": 5, "following": 10 } ...`
+
+**Example 2: using range-based aggregation**
+```php
+$qb->window(['preceding' => 5, 'following' => 10], 't.time')
+``` 
+Resulting AQL: `... WINDOW t.time WITH { "preceding": 5, "following": 10 } ...`
+
+[ArangoDB WINDOW documentation](https://www.arangodb.com/docs/stable/aql/operations-window.html)
+
+
 ## Other clauses
 
 ### OPTIONS
diff --git a/src/AQL/HasDocumentFunctions.php b/src/AQL/HasDocumentFunctions.php
index 40358a1..6b521e5 100644
--- a/src/AQL/HasDocumentFunctions.php
+++ b/src/AQL/HasDocumentFunctions.php
@@ -89,10 +89,10 @@ public function matches(
      *
      * @link https://www.arangodb.com/docs/stable/aql/functions-document.html#merge
      *
-     * @param  array<mixed>  $documents
+     * @param  array<mixed>|string|Expression  $documents
      * @return FunctionExpression
      */
-    public function merge(array ...$documents): FunctionExpression
+    public function merge(string|array|Expression ...$documents): FunctionExpression
     {
         return new FunctionExpression('MERGE', $documents);
     }
diff --git a/tests/Unit/AQL/DocumentFunctionsTest.php b/tests/Unit/AQL/DocumentFunctionsTest.php
index 9f9985e..3518b5a 100644
--- a/tests/Unit/AQL/DocumentFunctionsTest.php
+++ b/tests/Unit/AQL/DocumentFunctionsTest.php
@@ -69,6 +69,29 @@ public function testMerge()
         self::assertEquals('RETURN MERGE({"user1":{"name":"Janet"}}, {"user2":{"name":"Tom"}})', $qb->get()->query);
     }
 
+    public function testMergeVariable()
+    {
+        $qb = new QueryBuilder();
+
+        $qb->for('u', 'users')
+            ->return(
+                $qb->merge(
+                    'u',
+                    [
+                        'user1' => ['name' => 'Janet']
+                    ],
+                    [
+                        'user2' => ['name' => 'Tom']
+                    ]
+                )
+            );
+
+        self::assertEquals(
+            'FOR u IN users RETURN MERGE(u, {"user1":{"name":"Janet"}}, {"user2":{"name":"Tom"}})',
+            $qb->get()->query
+        );
+    }
+
     public function testMergeWithArrayOfDocuments()
     {
         $qb = new QueryBuilder();