Pronunciation: (är),[key] —n., —pl.R's or Rs, r's or rs. 1. the 18th letter of the English alphabet, a consonant.
2. any spoken sound represented by the letter R or r, as in ran, carrot, or rhyme. 3. something having the shape of R. 4. a written or printed representation of the letter R or r. 5. a device, as a printer's type, for reproducing the letter R or r. 6. See three R's.
3. regular: a man's suit or coat size.
5. restricted: a rating assigned to a motion picture by the Motion Picture Association of America indicating that children under the age of 17 will not be admitted unless accompanied by an adult. Cf. G (def. 7), PG, PG–13, X. [abbrev. for restricted]
6. Theat.stage right.
—Symbol. 1. the 18th in order or in a series, or, when I is omitted, the 17th.
2. (sometimes l.c.) the medieval Roman numeral for 80. Cf. Roman numerals. 3. Biochem.arginine.
4. Physics.See universal gas constant. 5. registered trademark: written as superscript ® following a name registered with the U.S. Patent and Trademark Office.
Ecol. the theoretical intrinsic rate of increase of a population, equivalent to the difference between the birth and death rates divided by the number of individuals in the population. Also called Malthusian parameter.