# อาร์
## Noun (N)
### Sense: the length of a line segment between the center and circumference of a circle or sphere
- radius
- r
### Sense: the 18th letter of the Roman alphabet
- R
### Sense: (physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole
- gas constant
- universal gas constant
### Sense: a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
- roentgen