An adage is a short, but memorable saying, which holds some important fact of experience that is considered true by many people, or it has gained some credibility through its long use.

Adages may be interesting observations, practical or ethical guidelines, or pessimistic comments on life. Some adages are products of folk wisdom which attempt to summarize some basic truth; these are generally known as proverbs. An adage which describes a general rule of conduct may be known as a "maxim". A pithy expression which has not necessarily gained credit through long use but which is distinguished by particular depth or good style is known as an aphorism, while one distinguished by wit or irony is known as an epigram. Through overuse, an adage may become a cliché or truism.

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 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 which develop in internet fora or Usenet newsgroups, are known for generating their own adages.

List of some modern adages

(For a listing of old adages, see proverb.)

Famous adages from science fiction:

• Amara's law: We tend to overestimate the effect of a technology in the short run and underestimate the effect in the long run.
• Clarke's three laws:
  • When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
  • The only way of discovering the limits of the possible is to venture a little way past them into the impossible.
  • Any sufficiently advanced technology is indistinguishable from magic.
• TANSTAAFL: There ain't no such thing as a free lunch.

Famous adages from Usenet:

• Godwin's law: As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.
• Ugol's law : If you ever ask "am I the only one who has this kink?" the answer is invariably "no".

Famous work-related adages:

• Peter principle: In a hierarchy every employee tends to rise to his level of incompetence.
• Dilbert Principle: In a company, the most ineffective workers are systematically moved to the place where they can do the least damage: management.
• Parkinson's law: Work expands so as to fill the time available for its completion.

Other famous adages:

• Murphy's law: If anything can go wrong, it will.
• Finagle's law: Anything that can go wrong, will.
• Sturgeon's law: Ninety percent of everything is crud.
• Hanlon's razor: Never attribute to malice that which can be adequately explained by stupidity.
• Laws of infernal dynamics:
  • An object in motion will be moving in the wrong direction.
  • An object at rest will be in the wrong place.
  • The energy required to move an object in the correct direction, or put it in the right place, will be more than you wish to expend but not so much as to make the task impossible.
• Law of accumulation: Everything great and worthwhile in human life is an accumulation of hundreds and sometimes thousands of tiny efforts and sacrifices that nobody ever sees or appreciates.
• Okrent's law : The pursuit of balance can create imbalance because sometimes something is true.
• Law of conservation of misery: Misery is never created or destroyed, just transformed.