A neutrino is a subatomic particle that is part of the Standard Model of particle physics. It is electrically neutral, has an incredibly small mass (which is still not precisely measured but is known to be much less than that of an electron), and interacts very weakly with other matter, meaning it can pass through ordinary matter almost undetected.
Articles by others on the same topic
A neutrino is an electrically neutral spin-one-half lepton. The Standard Model has three active neutrino flavours associated with the electron, muon and tau.
First observed directly by the Cowan-Reines neutrino experiment.