1. rabbi.
2. Radical.
3. radius.
4. railroad.
5. railway.
6. (in South Africa) rand; rands.
7. Réaumur.
8. Also, R (in prescriptions) take. [ recipe ]
9. rector.
10. redactor.
11. regina.
12. Republican.
13. response.
14. rex.
15. river.
16. road.
17. royal.
18. ruble.
19. rupee.
20. Theat. stage right.