radon

n.氡

radio transmitter, radio-, radio-astronomer, radio-carbon, radio-controlled, radio-frequency, radio-therapist, radio-therapy, radioactive, radioactivity, radiogram, radiograph, radiographer, radiography, radioisotope, radiologist, radiology, radish, radium, radius, RAF, raffia, raffish, raffishly, raffishness, raffle, raft, rafter, raftered, rag, rag-and-bone man, rag-bag, ragamuffin, rage, ragged, raggedly, raggedness, raging, raglan, ragout,