Update docs/source/user-guide/expressions.md

Co-authored-by: comphead <[email protected]>

docs/source/user-guide/expressions.md

@@ -237,7 +237,7 @@ Unlike to some databases the math functions in Datafusion works the same way as
 | array_replace_all(array, from, to)    | Replaces all occurrences of the specified element with another specified element. `array_replace_all([1, 2, 2, 3, 2, 1, 4], 2, 5) -> [1, 5, 5, 3, 5, 1, 4]`              |
 | array_slice(array, index)             | Returns a slice of the array. `array_slice([1, 2, 3, 4, 5, 6, 7, 8], 3, 6) -> [3, 4, 5, 6]`                                                                              |
 | array_to_string(array, delimiter)     | Converts each element to its text representation. `array_to_string([1, 2, 3, 4], ',') -> 1,2,3,4`                                                                        |
-| array_union(array1, array2)           | CReturns an array of the elements in the union of array1 and array2 without duplicates. `array_union([1, 2, 3, 4], [5, 6, 3, 4]) -> [1, 2, 3, 4, 5, 6]`
+| array_union(array1, array2)           | Returns an array of the elements in the union of array1 and array2 without duplicates. `array_union([1, 2, 3, 4], [5, 6, 3, 4]) -> [1, 2, 3, 4, 5, 6]`
 | cardinality(array)                    | Returns the total number of elements in the array. `cardinality([[1, 2, 3], [4, 5, 6]]) -> 6`                                                                            |
 | make_array(value1, [value2 [, ...]])  | Returns an Arrow array using the specified input expressions. `make_array(1, 2, 3) -> [1, 2, 3]`                                                                         |
 | trim_array(array, n)                  | Deprecated                                                                                                                                                               |