Defamation is a communication that injures a third party's reputation and causes a legally redressable injury. The precise legal definition of defamation varies from country to country. It is not necessarily restricted to making assertions that are false, and can extend to concepts that are more abstract than reputation such as dignity and honour.
In the English-speaking world, the law of defamation traditionally distinguishes between libel (written, printed, posted online, published in mass media) and slander (oral speech). It is treated as a civil wrong (tort, delict), as a criminal offence, or both.