| Abbreviation | Definition |
|---|---|
| R | Registered |
| RAP | Retail Analysis Program |
| RAPS | Rural Adjustment Processing System |
| RCA | Rural Carrier Associate |
| RCSC | Rates and Classification Service Center |
| RD | Road |
| RDR | Rural Delivery Route |
| RE | Reunion |
| REAR | Rear |
| RECV | Received |
| REDRESS | Resolve Employment Disputes Reach Equitable Solutions Swiftly® |
| RLO | Return Letter Office |
| RM | Room |
| RO | Romania |
| RPW | Revenue, Pieces, and Weight |
| RR | Rural Route |
| RS | Serbia |
| RSC | Rigid Steel Container |
| RSVP | Reply Soon Via Post |
| RT | Route |