摘要: We summarize the experiments on the 17 Kev/c~2 neutrino since 1985 and discuss possible mass term of the neutrino. Various extensions of the minimal standard model to accommodate a finite neutrino mass and the status of the massive neutrino phenomenology are summarized. Finally the meaning of the 17 KeV/c~2 neutrino is discussed. The purpose of this article is to collect the known relevant materials and to make a pedagogical summary of the interesting possibility of a heavy neutrino which will have far-reaching implications if it is eventually confirmed.