- roentgen, R - a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
--1 is a kind of radioactivity unit
- Roentgen, Wilhelm Konrad Roentgen, Rontgen, Wilhelm Konrad Rontgen - German physicist who discovered x-rays and developed roentgenography (1845-1923)
--2 is a kind of physicist