Also known as surfactant. A substance that can significantly alter (usually reduce) the interfacial tension of a liquid or the interfacial tension between two phases. The non-polar group containing both hydrophilic polar groups and hydrophobic water in the molecule tends to concentrate in the liquid at the interface between the liquid and the other phase, forming a thin molecular film and lowering the tension, thereby generating a moisture. Wet, emulsification, dispersion, foaming and other effects. Many types, mainly anionic, cationic and non-ionic three major categories.