Sterile neutrinos are considered as a candidate for dark matter in the context of the standard electroweak theory. This model suggests that sterile neutrinos, which do not interact via the weak force, could be the dark matter. Their production is primarily through neutrino oscillations, and they may not be in thermal equilibrium with the early universe. However, they can still influence the dynamics of the universe and contribute to the missing mass needed for closure. The paper discusses the implications of sterile neutrinos as dark matter, focusing on their mass and how they affect the structure formation in the universe. It considers a single generation of neutrino fields with a Dirac mass and a Majorana mass for the right-handed components. The number density of sterile neutrinos is proportional to μ²/M, making the energy density today independent of M. However, M is crucial for determining the large-scale structure of the universe. The paper also compares different dark matter models, including cold dark matter (CDM), hot dark matter (HDM), and the combination of cold and hot dark matter (C+HDM). It notes that C+HDM may offer advantages over both CDM and HDM in explaining structure formation. However, from a particle physics perspective, the existence of multiple dark matter types implies new physics beyond the standard model. The paper proposes a realistic warm dark matter candidate, where sterile neutrinos are heavier but less abundant than usual HDM neutrinos. This warm dark matter model may have advantages over both hot and cold dark matter scenarios. The paper calculates the number density of sterile neutrinos and their contribution to the energy density of the universe. It also discusses the evolution of perturbations in a universe dominated by sterile neutrinos, noting that the power on scales of order 1–5 Mpc is less than in CDM but greater than in HDM. The paper concludes that sterile neutrinos can serve as a viable warm dark matter candidate, with several advantages over cold or hot dark matter models. It also notes that the presence of sterile neutrinos could lead to an increase in the predicted primordial helium abundance, which could be detectable. The paper highlights the importance of considering the effects of sterile neutrinos on the large-scale structure of the universe and their potential role in explaining observed cosmological data.Sterile neutrinos are considered as a candidate for dark matter in the context of the standard electroweak theory. This model suggests that sterile neutrinos, which do not interact via the weak force, could be the dark matter. Their production is primarily through neutrino oscillations, and they may not be in thermal equilibrium with the early universe. However, they can still influence the dynamics of the universe and contribute to the missing mass needed for closure. The paper discusses the implications of sterile neutrinos as dark matter, focusing on their mass and how they affect the structure formation in the universe. It considers a single generation of neutrino fields with a Dirac mass and a Majorana mass for the right-handed components. The number density of sterile neutrinos is proportional to μ²/M, making the energy density today independent of M. However, M is crucial for determining the large-scale structure of the universe. The paper also compares different dark matter models, including cold dark matter (CDM), hot dark matter (HDM), and the combination of cold and hot dark matter (C+HDM). It notes that C+HDM may offer advantages over both CDM and HDM in explaining structure formation. However, from a particle physics perspective, the existence of multiple dark matter types implies new physics beyond the standard model. The paper proposes a realistic warm dark matter candidate, where sterile neutrinos are heavier but less abundant than usual HDM neutrinos. This warm dark matter model may have advantages over both hot and cold dark matter scenarios. The paper calculates the number density of sterile neutrinos and their contribution to the energy density of the universe. It also discusses the evolution of perturbations in a universe dominated by sterile neutrinos, noting that the power on scales of order 1–5 Mpc is less than in CDM but greater than in HDM. The paper concludes that sterile neutrinos can serve as a viable warm dark matter candidate, with several advantages over cold or hot dark matter models. It also notes that the presence of sterile neutrinos could lead to an increase in the predicted primordial helium abundance, which could be detectable. The paper highlights the importance of considering the effects of sterile neutrinos on the large-scale structure of the universe and their potential role in explaining observed cosmological data.