I'm confused about the term "sterile neutrino". I always thought it meant right-handed fields that would be paired with the three known left-handed neutrino fi

I'm confused about the term "sterile neutrino". I always thought it meant right-handed fields that would be paired with the three known left-handed neutrino fields if they were Dirac fermions. In this way they would not be seen as distinct particles below electro-weak symmetry breaking. This article and many others imply that sterile neutrinos are a "fourth generation" particle that would show up as a missing signal in oscillation experiments. Can any particle physicists browsing here that could clarify?