| Reusability - | (Software Engineering) the ability to reuse an already-existing program component in another application |
| Reusable components - | (Software Engineering) configuration items that are reusable |
| Reverse engineering - | (Software Engineering) trying to develop design models or an understanding of design using program code as a starting point |
| Risk - | (Software Engineering) a potential problem or occurrence that put a project in jeopardy |
| Risk analysis - | (Software Engineering) a techniques for identifying and evaluating risks |
| Risk Management and Monitoring Plan (RMMP) - | (Software Engineering) a plan for mitigating, monitoring and managing risks |
| Rebound | (Concrete Engineering) Wet shotcrete or sand and cement which bounces away from a surface again at which pneumatically applied mortar is being projected. |
| Reinforced Concrete (RC) | |
| Retardation | (Concrete Engineering) Delaying the hardening or strength gain of fresh concrete, mortar or grout. |
| Retempering | (Concrete Engineering) The addition of water and remixing of concrete which has started to stiffen: usually not allowed as it may affect the ultimate strength. |