Miscible liquids combine to form a suspension in which the total fluid volume contains roughly equal parts of the two component liquids, while immiscible liquids do not mix. When two immiscible liquids are put into the same container, they form distinct layers with a clear border.
An example of immiscible liquids is water and oil. Oil is nonpolar, and it does not dissolve in water. Alcohol, however, is polar and mixes completely with water. Some fluids are partially miscible and mix incompletely. An example of partially miscible liquids is water and organic acids. These liquids mix, but the mixture is not complete, and the solution separates into two layers with only small quantities of each substance on the opposite side.