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r 音标拼音: ['ɑr] n. 字母 r字母 rR n 1: a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air [ synonym: { roentgen}, { R}] 2: ( physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8. 3143 joules per kelvin per mole [ synonym: { gas constant}, { universal gas constant}, { R}] 3: the 18th letter of the Roman alphabet [ synonym: { R}, { r}] 4: the length of a line segment between the center and circumference of a circle or sphere [ synonym: { radius}, { r}] R \ R\ ([ aum] r). R, the eighteenth letter of the English alphabet, is a vocal consonant. It is sometimes called a semivowel, and a liquid. See Guide to Pronunciation, [ sect][ sect] 178, 179, and 250- 254. " R is the dog' s letter and hurreth in the sound." -- B. Jonson. [ 1913 Webster] Note: In words derived from the Greek language the letter h is generally written after r to represent the aspirated sound of the Greek " r, but does not affect the pronunciation of the English word, as rhapsody, rhetoric. [ 1913 Webster] The English letter derives its form from the Greek through the Latin, the Greek letter being derived from the Ph[ oe] nician, which, it is believed, is ultimately of Egyptian origin. Etymologically, R is most closely related to l, s, and n; as in bandore, mandole; purple, L. purpura; E. chapter, F. chapitre, L. capitulum; E. was, were; hare, G. hase; E. order, F. ordre, L. ordo, ordinis; E. coffer, coffin. [ 1913 Webster] { The three Rs}, a jocose expression for reading, ( w) riting, and ( a) rithmetic, -- the fundamentals of an education. [ 1913 Webster] |
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