Defect
A characteristic, factor, or aspect of a product, process, service, or system that renders it nonconforming – e.g., inaccurate, inoperable, or of less than acceptable quality. Defects can be categorized into four "classes":
1) "very serious," i.e., causing "severe" physical and/or economic harm;
2) "serious," i.e., causing "significant" physical or economic harm;
3) "major," i.e., causing substantial problems or difficulties with the unit's intended use; and
4) "minor," i.e., causing relatively inconsequential problems or difficulties with the unit's intended use.