Although you can type in any language in an Excel 2013 workbook, the program itself assumes you're writing and reading in English, and uses English both for features such as spell checking and in the menus and dialog boxes. To change to a new language, download the language interface pack and activate it in Excel.
Visit Microsoft's Office language interface pack Web page (link in Resources) and download a pack for the language you want. Save your work and close any open Office programs, and then run the download to install the language.
Open Excel, open the "File" menu and click "Options."
Switch to the "Language" tab and pick the new language in the Choose Editing Languages box. Press "Set as Default" and then click "Yes" to acknowledge the warning that some of your settings might change. Do not quit and restart Excel yet.
Select the new language in both the Display Language and Help Language boxes and press the "Set as Default" button under each.
Click "OK," and then click "OK" on the message about restarting Office. Save any open work and close all Office programs.
Reopen Excel to begin working in the new language.