Lather, rinse, repeat (sometimes wash, rinse, repeat) is an
idiom
An idiom is a phrase or expression that typically presents a figurative, non-literal meaning attached to the phrase; but some phrases become figurative idioms while retaining the literal meaning of the phrase. Categorized as formulaic language, ...
roughly quoting the instructions found on many brands of
shampoo
Shampoo () is a hair care product, typically in the form of a viscous liquid, that is used for cleaning hair. Less commonly, shampoo is available in solid bar format. Shampoo is used by applying it to wet hair, massaging the product into the ...
. It is also used as a humorous way of pointing out that such instructions, if taken literally, would result in an
endless loop
, also called Eiko or Peko, is a female J-pop singer-songwriter, and producer who is currently affiliated with Heart Company. She is best known for singing the opening themes of the anime series ''Higurashi When They Cry''. Eiko also handles a s ...
of repeating the same steps, at least until one runs out of shampoo. It is also a sarcastic
metaphor
A metaphor is a figure of speech that, for rhetorical effect, directly refers to one thing by mentioning another. It may provide (or obscure) clarity or identify hidden similarities between two different ideas. Metaphors are often compared wit ...
for following instructions or procedures slavishly without critical thought.
With modern shampoo, the first use is normally sufficient to clean hair. However, if the hair was very dirty then the first use will ''not'' result in a lot of lather. The second use then creates a lot more lather, which feels and looks good and gives the impression that the shampoo is somehow doing more useful activity, when in fact the first use was all that was really needed. The result is use, and purchase over time, of twice as much shampoo as is really needed.
It is known as the shampoo algorithm, and is a classic example of an
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
in introductory
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
classes.
In
Benjamin Cheever
Benjamin Hale Cheever (born October 8, 1948) is an American writer and editor. He is the son of Mary Winternitz and writer John Cheever and brother of Susan Cheever. To date, he has written four adult fiction novels, one children's book, and tw ...
's novel ''The Plagiarist'', a fictional advertising executive increases the sales of his client's shampoo by adding the word "repeat" to its instructions.
See also
*
Hair washing
Hair washing is the cosmetic act of keeping hair clean by washing it. To remove sebum from hair, some apply a surfactant, usually shampoo (sometimes soap) to their hair and lather the surfactant with water. The surfactant is rinsed out with water ...
References
English phrases
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