In the solution process, the terms soluble and miscible refer to solids dissolved in liquids and liquids dissolved in liquids, respectively. A solid substance that dissolves completely in a given solvent is said to be soluble. Sodium chloride (NaCl) or salt is soluble in water. Two liquids that completely mix in each other are said to be miscible. Acetic acid is miscible in water.

Solutes and solvents that do not mix appreciably are called insoluble and immiscible. Examples of these are margarine, which is insoluble in water, and oil, which is immiscible in water.