This paper presents a study of the rotation curves (RCs) of spiral galaxies, revealing a universal relationship between the rotation velocity and the luminosity of the galaxy. Using a sample of about 1100 optical and radio RCs, the authors confirm that the rotation velocity at any radius depends on the galaxy's luminosity, indicating the presence of dark matter (DM). At high luminosities, the RCs show a slight discrepancy between the observed and predicted velocities from luminous matter (LM), implying a small amount of DM. At low luminosities, the LM prediction fails significantly, and DM becomes the dominant mass component. The study shows that the universal RC implies specific scaling relationships between DM and LM parameters. These include the DM/LM mass ratio decreasing with luminosity, the central halo density scaling with luminosity, the halo core radius being comparable to the optical radius but shrinking at low luminosities, and the total halo mass scaling with luminosity. These relationships are represented as a curve in a four-dimensional space, showing the tight coupling between DM and LM in spiral galaxies. The paper also discusses the implications of these findings for galaxy formation theories. It shows that the RC shapes are strongly dependent on luminosity, with low-luminosity galaxies having steeper RCs and high-luminosity galaxies having flatter RCs. This dependence suggests that the structural properties of DM and LM are connected, likely due to the process of galaxy formation itself. The authors derive the universal rotation curve and show that it can be represented by a mathematical function that accurately describes the observed RCs. This function accounts for the contributions of both the stellar disc and the dark halo, with the dark halo playing a significant role in the outer regions of the galaxy. The study also highlights the importance of the universal rotation curve in understanding the distribution of dark matter in spiral galaxies and its relationship to luminous matter. The findings support the idea that dark matter is a significant component of spiral galaxies, especially at low luminosities, and that the distribution of dark matter is different from that of luminous matter. The results have important implications for understanding the formation and evolution of galaxies.This paper presents a study of the rotation curves (RCs) of spiral galaxies, revealing a universal relationship between the rotation velocity and the luminosity of the galaxy. Using a sample of about 1100 optical and radio RCs, the authors confirm that the rotation velocity at any radius depends on the galaxy's luminosity, indicating the presence of dark matter (DM). At high luminosities, the RCs show a slight discrepancy between the observed and predicted velocities from luminous matter (LM), implying a small amount of DM. At low luminosities, the LM prediction fails significantly, and DM becomes the dominant mass component. The study shows that the universal RC implies specific scaling relationships between DM and LM parameters. These include the DM/LM mass ratio decreasing with luminosity, the central halo density scaling with luminosity, the halo core radius being comparable to the optical radius but shrinking at low luminosities, and the total halo mass scaling with luminosity. These relationships are represented as a curve in a four-dimensional space, showing the tight coupling between DM and LM in spiral galaxies. The paper also discusses the implications of these findings for galaxy formation theories. It shows that the RC shapes are strongly dependent on luminosity, with low-luminosity galaxies having steeper RCs and high-luminosity galaxies having flatter RCs. This dependence suggests that the structural properties of DM and LM are connected, likely due to the process of galaxy formation itself. The authors derive the universal rotation curve and show that it can be represented by a mathematical function that accurately describes the observed RCs. This function accounts for the contributions of both the stellar disc and the dark halo, with the dark halo playing a significant role in the outer regions of the galaxy. The study also highlights the importance of the universal rotation curve in understanding the distribution of dark matter in spiral galaxies and its relationship to luminous matter. The findings support the idea that dark matter is a significant component of spiral galaxies, especially at low luminosities, and that the distribution of dark matter is different from that of luminous matter. The results have important implications for understanding the formation and evolution of galaxies.