Monophasic liquid refers to a substance (usually a solution) that possesses a uniform physical and chemical composition throughout. It does not have different layers or phases of different compositions, unlike heterogenous mixtures. Monophasic liquids can be further classified into two types: homogeneous and isotropic.

Homogeneous monophasic liquids have a consistent concentration and distribution of solute molecules in the solvent. Examples of homogeneous monophasic liquids include solutions of common household cleaning products, such as bleach or dish soap.

Isotropic monophasic liquids show the same physical characteristics in all directions. These types of liquids have no preferred orientation of their molecules or atoms. Examples of isotropic monophasic liquids include cooking oils, gasoline, and motor oil.

Monophasic liquids can be distinguished from biphasic and multiphasic liquids based on their physical properties, such as viscosity, density, and solubility. Understanding the properties of monophasic liquids is essential in fields such as chemistry, biology, and environmental science, where solutions and other liquid-based substances are commonly used.