Change a label for a report without changing the label for the underlying table

To change a label for a column in a report only, without changing the label for the underlying table in the system dictionary, create a custom database view to use as the report source and create a new language file entry for the label.

Any

Steps:

1. From Filter navigator > Reports > View Run, identify the report source. If the report source is a database view, proceed to step 2. Otherwise, create a new database view to use as the report source.
2. Identify the variable prefix and the name of the field on the database view.
3. Create a new entry from System Definition > Language File. The element field should contain the name of the variable prefix and the name of the field on the database view.

For example:
1. Create your database view and make note of the table prefixes for the tables included in the database view
2. In the Field Navigator, go to System Definition --> Language File
3. Create a New entry in the Language File here:
- In here
Table = Database View name
Label = Name of the field/column name you want to rename the field/column as
Element = in the format <viewtableprefix_fieldname>
--> (example - inc_num where inc is the prefix of the table in my database view and num is the view field)
4. Save/Submit this record
5. Add another record for the other column name if needed , following steps 2 to 4 above.  

Please see the documentation on Database Views