Corrective maintenance (CM) can be defined as a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or asset can be restored to an operational condition within the tolerances or limits established for in-service operations.

Corrective maintenance is maintenance which is carried out after failure detection and is aimed at restoring an asset to a condition in which it can perform its intended function.

Preventive maintenance (PM) has the following meanings:
The care and servicing provided by qualified personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by means of systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects.