R

I. abbreviation 1. rabbi 2. radial 3. radical — used especially of a monovalent hydrocarbon radical 4. Rankine 5. Reaumur 6. recipe 7. registered trademark — often enclosed in a circle 8. regular 9. Republican 10. river 11. R-value II. certification mark — used to certify that a motion picture is of such a nature that admission is restricted to persons over a specified age (as 17) unless accompanied by a parent or guardian; compare g, NC-17, pg, PG-13