Diluents are substances used to reduce the concentration of a solution or mixture. They are commonly added to liquids to make them less potent or to achieve a desired consistency. For example, in pharmaceuticals, water or saline can be used as diluents to prepare medications for injection. In various industries, such as paint and cosmetics, diluents help in adjusting the viscosity and improving the application properties of products. They ensure that the final product meets specific performance criteria while maintaining safety and effectiveness.