| Term | Definition | Contributor | Modified |
|---|---|---|---|
| rudimentary | A type of sunspot penumbra characterized by granular (rather than filamentary) structure, brighter intensity than the umbra, and narrow extent, and possibly only partially surrounding the umbra. Penum brae are typically rudimentary during the sunspot formative and decay phases. | Ryan McGranaghan | 2023.04.16 |
| Rugby (Dice game) | No definition provided | Christopher Rauch | 2023.12.01 |
| Rugs | No definition provided | Christopher Rauch | 2023.12.01 |
| Rugs, Oriental | No definition provided | Christopher Rauch | 2023.12.01 |
| Rugs, Persian | No definition provided | Christopher Rauch | 2023.12.01 |
| Ruifrancoite | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Ruins | No definition provided | Christopher Rauch | 2023.12.01 |
| Ruitenbergite | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Ruizite | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Rule in Shelley’s case | No definition provided | Christopher Rauch | 2023.12.01 |
| Rule of the road | No definition provided | Christopher Rauch | 2023.12.01 |
| Rule of the road at sea | No definition provided | Christopher Rauch | 2023.12.01 |
| Rulers | No definition provided | Christopher Rauch | 2023.12.01 |
| Rules and logic | No definition provided | Ryan McGranaghan | 2023.04.16 |
| Rules of order | No definition provided | Christopher Rauch | 2023.12.01 |
| Rum | No definition provided | Christopher Rauch | 2023.12.01 |
| Rumanian | No definition provided | Christopher Rauch | 2023.12.01 |
| Rumanian language | No definition provided | Christopher Rauch | 2023.12.01 |
| Rumanian language--Bibl | No definition provided | Christopher Rauch | 2023.12.01 |
| Rumanian literature | No definition provided | Christopher Rauch | 2023.12.01 |