What is the difference between ECN and ECO in engineering change management?

An ECO (Engineering Change Order) is a document requesting a change to a product design, specifying what needs to change and why. An ECN (Engineering Change Notice) is the notification or implementation document that communicates the approved change to all affected departments. The ECO initiates the change process, while the ECN announces its implementation. Some organizations use these terms interchangeably or combine them.