R


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R,

18th letter of the alphabetalphabet
[Gr. alpha-beta, like Eng. ABC], system of writing, theoretically having a one-for-one relation between character (or letter) and phoneme (see phonetics). Few alphabets have achieved the ideal exactness.
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, corresponding to Greek rho. When in Latin alphabets the letters for p and r became similar in appearance, the rho form (P; which at first was used for the r sound) was restricted to the p sound, and an extra line was added for the r sound (R). In Greek, where no confusion developed, the rho continued to look like Latin P. A modification of R is the symbol ℞, used medically for recipe [Lat.,=take] and liturgically for responsum [Lat.,=response].

r

(nucleonics)

R

(nucleonics)

R

1. Abbr. for “radius.”
2. Abbr. for “right.”
3. Symbol for the capacity of a pile (for example, 3R indicates three times design capacity).
4. Symbol for the thermal resistance of a material or component of construction.
5. Symbol for electrical resistance.

sound reduction index, R

British term for sound transmission loss.