“Occurrence” is the general term for both accidents and incidents.
An accident would be, for example, the occurrence in Toronto where the aircraft flipped upside down on landing. That would be an accident—a major one.
An incident would be an engine failure, such as an aircraft's having an engine failure and having to do an emergency landing at an airport, but with no damage, no injuries or any of that—just engine failure and an emergency landing. That would be an incident.