The "MRO" acronym has two different spell-outs, depending on the situation. Organizations like power generation plants (utilities) and manufacturers with large, complex plants need to keep the facilities in good repair. This activity is called "Maintenance, Repair, and Operations." This also includes building and equipment maintenance for Schools, Office buildings, Hospitals, Hotels, Apartment complexes, etc.

Organizations with fleets of transportation equipment (air planes, railroad cars, trucks, or automobiles) need "Maintenance, Repair, and Overhaul" service to keep this equipment in good working order. Common usage refers to the parts used for MRO as "spare parts," rather than "service parts."