An adage (/ˈædᵻdʒ/; Latin: adagium) is a short, usually philosophical, but memorable saying which holds some important fact of experience that is considered true by many people, or that has gained some credibility through its long memetic use.
It often involves a planning failure such as "don't count your chickens before they hatch" or "don't burn your bridges". Adages may be interesting observations, practical or ethical guidelines, or skeptical comments on life.
Some adages are products of folk wisdom that attempt to summarize some form of basic truth; these are generally known as proverbs or bywords. An adage that describes a general rule of conduct is a "maxim". A pithy expression that has not necessarily gained credit through long use, but is distinguished by particular depth or good style is an aphorism, while one distinguished by wit or irony is an epigram.
Through overuse, an adage may become a cliché or truism, or be described as an "old saw." Adages coined in modernity are often given proper names and called "laws" in imitation of physical laws, or "principles". Some adages, such as Murphy's Law, are first formulated informally and given proper names later, while others, such as the Peter Principle, have proper names in their initial formulation; it might be argued that the latter sort does not represent "true" adages, but the two types are often difficult to distinguish.
Adages which were collected and used by ancient writers in their work and writings inspired the Dutch humanist scholar Desiderius Erasmus to publish his own collection. He would revise his moderate volume of 800 adages multiple times until the final edition of Adagia published in 1536 included over 4,000. There have been many such collections since, usually in vernacular languages.
Adages formulated in popular works of fiction often find their way into popular culture, especially when there exists a subculture devoted to the work or its genre, as is the case with science fiction novels. Many professions and subcultures create their own adages, which may be seen as a sort of jargon; such adages may find their way into popular usage, sometimes becoming altered in the process. Online communities, such as those that develop in Internet forums or Usenet newsgroups, are known for generating their own adages.