Any of various surfactants (substances that reduce surface tension) used to dislodge dirt from soiled surfaces and retain it in suspension, allowing it to be rinsed away. The term usually refers to synthetic substances and excludes soaps. The characteristic features of a molecule of any detergent are a hydrophilic (water-attracting) end and a hydrophobic (oil-attracting) end. In ionic detergents, the hydrophilic property is conferred by the ionized part of the molecule. In nonionic detergents, hydrophilicity is based on the presence of multiple hydroxyl groups or other hydrophilic groups. Besides those used in water to clean dishes and laundry, detergents that function in other solvents are used in lubricating oils, gasolines, and dry-cleaning solvents to prevent or remove unwanted deposits. They are also used as emulsifying agents (see emulsion).
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Often people use soaps and detergents assist in the emulsification of oils and dirt particles so they can be washed away.
People usually wash themselves periodically. Little children, the sick, and people with disabilities may be washed by a caregiver. Often a shower or a bathtub is used for persons washing themselves or others. Showers or baths are commonly taken in the nude and often in private.
More frequent is washing of just the hands, e.g. before and after preparing food and eating, after using the toilet, after handling something dirty, etc. Hand washing is important in reducing the spread of germs.
Brushing one's teeth is also a kind of washing.