R

1. Raffinose
2. Rain water
3. Raspberry
4. Rb⁺, Rubidium
5. Rebaudioside A
6. Resorcinol
7. Retinol, Vitamin A
8. Retinol acetate, Vitamin A acetate
9. Retinol palmitate, Vitamin A palmitate
10. Rhamnose
11. Ribavirin
12. Ribitol
13. Riboflavin, Vitamin B₂
14. Ribonuclease
15. Ribose
16. River water
17. RNA, Ribonucleic acid
18. tRNA, Transfer ribonucleic acid
19. Rubber
20. Rubidium, Rb⁺
21. Rutinose