According to our current understanding of particle physics, neutrinos do have mass, although it was once believed that they were massless. Neutrinos are elementary particles that belong to the lepton family, along with electrons, muons, and taus. There are three types, or flavors, of neutrinos: electron neutrinos, muon neutrinos, and tau neutrinos.
Experimental evidence from neutrino oscillation experiments, such as the Super-Kamiokande and Sudbury Neutrino Observatory experiments, has provided strong indications that neutrinos have mass and can change from one flavor to another as they travel through space. This phenomenon of flavor oscillation implies that neutrinos must have different masses and that the neutrino flavors are mixtures of the neutrino mass states.
However, the absolute values of the masses of the three neutrino flavors are not precisely known, and determining them precisely is an active area of research in particle physics. Neutrinos are extremely elusive particles and interact only very weakly with matter, making their experimental study challenging. Various experiments, such as the Daya Bay and KamLAND experiments, are aimed at improving our understanding of neutrino properties, including their masses.