I. ˈär, ˈȧ noun
( plural r's or rs ˈärz, ˈȧz)
Usage: often capitalized, often attributive
1.
a. : the 18th letter of the English alphabet
b. : an instance of this letter printed, written, or otherwise represented
c. : a speech counterpart of orthographic r (as r in run, fry, arid, far-off, Spanish para, rey, French rire, or German rohr )
2. : a printer's type, a stamp, or some other instrument for reproducing the letter r
3. : someone or something arbitrarily or conveniently designated r especially as the 17th or when j is used for the 10th the 18th in order or class
4. : something having the shape of the letter R
5. capitalized : one of the three R's
controversy over the first R
II. abbreviation
Usage: often capitalized
1. rabbi
2. racemic
3. radical
4. radio
5. radius
6. railroad; railway
7. rain
8. range
9. rank
10. rare; rarity
11. ratio
12. real
13. rear
14. Reaumur
15. received
16. recipe
17. reconnaissance
18. recto
19. rector
20. red; reddish
21. refraction
22. refrigerator
23.
[Latin]
regina
24. registered
25. regulating
26. reigned
27. republic; republican
28. reserves
29. reside; residence; resident
30. resistance; resistor
31. respiration
32. respond; response
33.
[French retarder ]
slow
34. retired
35. retree
36. returning
37.
[Latin]
rex
38. rifle
39. right
40. ring
41. riser
42. rises
43. river
44. road
45. rod
46. roentgen
47. roman
48. rood
49. rook
50. rotor
51. rough
52. route
53. royal
54. rubber
55. ruble
56. rule
57. run
58. runic
59. rupee
III. symbol
1. correlation coefficient
2. capitalized gas constant
3. capitalized radical — used especially of a univalent hydrocarbon radical (as alkyl); compare general formula
4. capitalized recipe — often ℞
5. capitalized registered trademark — often enclosed in a circle
6. capitalized Reynolds number
7. capitalized Rydberg constant
8.
a. capitalized a relation in a logical or mathematical proposition
b. a proposition in a logical operation
IV. abbreviation
1. usually capitalized radial
2. repeat
3. rerun
V. symbol
1.
[probably from r ate ]
intrinsic rate of natural increase
2. capitalized the set of all real numbers