radiation /ˌreɪdiˈeɪʃən/ noun Learner's definition of RADIATION
[noncount]
1
: a type of dangerous and powerful energy that is produced by radioactive substances and nuclear reactions辐射 2
medical : the use of controlled amounts of radiation for the treatment of diseases (such as cancer)放射疗法；辐射疗法 — called also radiation therapy, radiotherapy
3
a : energy that comes from a source in the form of waves or rays you cannot see（波或射线的）辐射能 b technical : the process of giving off energy in the form of waves or rays you cannot see辐射的过程