Microsoft.Office.Core

Microsoft.Office.Core namespace

This namespace and assembly contains the core objects that are shared across all the different Office applications.
This reference can be added as a COM reference.

Office = Microsoft.Office.Core 

Office 365 - Microsoft Office 16 Object Library
Office 2019 - Microsoft Office 16 Object Library
Office 2016 - Microsoft Office 16 Object Library
Office 2013 - Microsoft Office 15 Object Library