Engineering change Note is used to refer to all changes which are needed either a specification change from a customer ( say, a revised drawing) or, organisation's own need after a process review.
Another instance could be a corrective/preventive actions arising out of a customer complaint.
ECN always results in an impact analysis to the processes affected by the change needed.
For an ISO/TS system, a re-validation followed by re-PPAP may also arise.
Any ECN prepared will result in impact to several system documents, say e.g
FMEA/Control Plan/WI/SOP etc.
As these are controlled documents in a QMS, any change to these documents are addressed through a Document Change Process ensuring a Revision History Record.