roentgen: a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
abstraction: a general concept formed by extracting common features from specific examples
centipede: chiefly nocturnal predacious arthropod having a flattened body of 15 to 173 segments each with a pair of legs, the foremost pair being modified as prehensors