| reclusive | Avoiding the company of other people; solitary | |
| recrudescent | Breaking out again; renewing | |
| rectitude | The quality of being honest and morally correct | |
| redouble | To become much greater, more intense, or more numerous | |
| redress | To set right; to remedy or rectify | |
| reductive | Tending to present a subject or problem in a simplified form, especially one viewed as crude. | |
| redundant | Not or no longer needed or useful; superfluous | |
| refracted | Measuring the bending of a ray of light or sound wave when it enters a medium where its speed is different | |
| refulgent | Shining very brightly | |
| rejuvenated | To make someone or something look or feel younger, fresher, or more lively | |