Detergent is a man-made or synthetic cleansing agent. As it is derived from petrochemicals (petroleum fractions), it is a "non-soap" cleansing agent. Detergents are normally sodium salts of sulphonic acid and they can be grouped into those with a benzene ring (sodium alkylbenzene sulphonate) and those without (sodium alkyl sulphate).

A detergent molecule dissociates in water to form:
o        sodium Na⁺ ions
o        detergent ions (sulphonate group / sulphate group)

The sulphonate group / sulphate group contains

o        the hydrophilic ionic "head" (which dissolves readily in water) and
o        the hydrophobic hydrocarbon "tail" (which dissolves readily in grease).