A diluent is a substance used to dilute or thin out another substance, often a liquid. It helps reduce the concentration of a solution, making it less potent or viscous. Common diluents include water, alcohol, and various solvents, depending on the application. In industries like pharmaceuticals and paints, diluents are essential for achieving the desired consistency and effectiveness. For example, in the preparation of medications, a diluent can help ensure that the active ingredients are evenly distributed and easier to administer.