Fix: An instance of Word, Outlook, or the Office Click-to-Run background service might still be active. Open Windows Task Manager, end all Office tasks, and launch the installer again as an administrator.
A Language Pack (also known as a Language Accessory Pack) is an add-on module that changes the display language of your Office applications, adds proofing tools (spell check, grammar, thesaurus), and localizes Help content. Microsoft Office 2016 Language Pack Offline Installer
Microsoft provides Language Accessory Packs for Office 2016. You can typically find these on the official Microsoft Support website. Fix: An instance of Word, Outlook, or the