Nexus is a framework for scaling Scrum. It is advisable to implement a framework like this in your organization when working with multiple Scrum Teams on a single product. Complexity and communication usually increase unnecessarily when multiple teams collaborate. This increase ultimately has a negative effect on the productivity and effectiveness of your teams. This is what you want to avoid.
The framework builds on Scrum by enhancing fundamental elements of Scrum. Nexus is ultimately aimed at minimizing dependencies between teams. In addition it assists in solving problems with collaboration and integration. Therefore the framework defines additional responsibilities, events and artifacts that connect the work of Scrum Teams in a Nexus. The framework was developed by Ken Schwaber and Scrum.org.
Definition of Nexus
The official definition of a Nexus is a group of approximately three to nine Scrum Teams that work together to deliver one product; it is a connection between people and things. A Nexus has one Product Owner who manages one Product Backlog from which the Scrum Teams work.
More information about the Nexus framework and how to implement it can be found in The Nexus™ Guide from Scrum.org.