The universal solvent is water. It is called so because it can dissolve more substances than any other liquid, making it crucial for numerous biological and chemical processes. Water's polar nature allows it to interact with various ionic and molecular compounds, facilitating reactions and transport in biological systems. This property is essential for life, as many biochemical reactions occur in aqueous solutions. Additionally, the role of water as a solvent is fundamental in environmental processes, such as nutrient cycling and pollution dynamics.