roentgen (also rontgen)

n unit of ionizing radiation (eg in X-rays) 伦琴（电离辐射单位, 如X射线的）.

rock-garden, rock-plant, rock-salt, rock-steady, rocker, rockery, rocket, rocketry, rockiness, rocking-chair (also rocker), rocking-horse, rocky, rococo, rod, rode, rodent, rodeo, rodomontade, roe, roebuck, Rogation Sunday, rogations, roger, rogue, roguery, rogues' gallery, roguish, roguishly, roguishness, roil, roister, roisterer, roistering, role, role (also role), role-play, roll, roll around, roll back, roll in,