Sorption is a physical and chemical process by which one substance becomes attached to another. Specific cases of sorption are treated in the following articles:

• Absorption – "the incorporation of a substance in one state into another of a different state" (e.g., liquids being absorbed by a solid or gases being absorbed by a liquid);
• Adsorption – the physical adherence or bonding of ions and molecules onto the surface of another phase (e.g., reagents adsorbed to a solid catalyst surface);
• Ion exchange – an exchange of ions between two electrolytes or between an electrolyte solution and a complex.