A radio supernova (RSN) is a supernova for which a radio signal has been detected. The term likely is used for supernovae in which radio has been detected early on: radio is not uncommon from supernova remnants. The early radio signal is of interest for revealing the mechanisms and evaluating theories regarding them. Such signals have been detected from core collapse supernovae but not Type Ia supernovae, though it is thought that they produce some. For the former, theory is that the radio emission is synchrotron radiation from ejecta interaction with the surrounding interstellar medium.