An engineering change notice (ECN) is a document used in engineering to inform stakeholders of changes made to a product or process. Some synonyms for ECN include engineering change order (ECO), modification notice, revision notice, change request, and update notice. These synonyms are used interchangeably based on the specific context of the engineering change. In some organizations, an ECN is a formal process whereas an ECO may be more informal. A modification notice may refer to a simple change, while a revision notice may imply a more significant update. Ultimately, the goal of these synonyms is to convey that an engineering change has been made and stakeholders need to be aware of it.