Graffiti (singular: graffito; the plural is used as a mass noun) is the name for images or lettering scratched, scrawled, painted or marked in any manner on property. Graffiti is often regarded by others as unsightly damage or unwanted vandalism.

Graffiti has existed since ancient times, with examples going back to Ancient Greece and the Roman Empire. Graffiti can be anything from simple scratch marks to elaborate wall paintings. In modern times, spray paint and markers have become the most commonly used materials. In most countries, defacing property with graffiti without the property owner's consent is considered vandalism, which is punishable by law. Sometimes graffiti is employed to communicate social and political messages. To some, it is an art form worthy of display in galleries and exhibitions. However, the public generally frowns upon "tags" that deface bus stops, trains, buildings, playgrounds and other public property.

"Graffiti" is applied in art history to works of art produced by scratching a design into a surface. A related term is "sgraffito," which involves scratching through one layer of pigment to reveal another beneath it. This technique was primarily used by potters who would glaze their wares and then scratch a design into it. Graffiti and graffito are from the Italian word graffiato ("scratched"). In ancient times, graffiti was carved on walls with a sharp object, although sometimes chalk or coal were used. The Greek infinitive γράφειν - graphein - means "to write."

Modern graffiti

Modern graffiti is often seen as having become intertwined with Hip-Hop culture as one of the four main elements of the culture (along with the Master of ceremony, the disc jockey, and break dancing), through Hollywood movies such as Wild Style. However, modern (twentieth century) graffiti predates hip hop by almost a decade and has its own culture, complete with its own unique style and slang.

For example, a famous graffiti of the 20th century was the inscription in the London subway reading "Clapton is God", in reference to the guitar skills of Eric Clapton. The phrase was spray-painted by an admirer on a wall in an Islington Underground station in the autumn of 1967. The graffiti was captured in a now-famous photograph, in which a dog is urinating on the wall. Similar approvals or disapprovals of musicians have continued since, for instance, the summer 2007 inscriptions in Harlem reading "50 Cent is Wack". A popular graffitos of the 1970s was the legend "Dick Nixon Before He Dicks You," reflecting the hostility of the youth culture to that U.S. president. The belief that graffiti and hip-hop are related arises from the fact that some graffiti artists enjoyed the other three aspects of hip-hop, and that it was mainly practiced in areas where the other three elements of hip-hop were evolving as art forms. Graffiti is recognized as a visual expression of the rap music of the decade, as breakdancing is the physical expression. Graffiti also became associated with the anti-establishment punk rock movement beginning in the 1970s. Bands such as Black Flag and Crass (and their followers) widely stenciled their names and logos, while many punk night clubs, squats and hangouts are famous for their graffiti.

Modern graffiti artists sometimes choose nicknames or "tags." Tags need to be quick to write, so they are often no more than 3 to 5 characters in length. A nickname is chosen to reflect personal qualities and characteristics, or because of the way the word sounds, and/or for the way it looks once written. The letters in a word can make execution difficult if the shapes of the letters don't naturally fit next to each other in a visually pleasing way. It's common for a graffiti artist to select a name that is a play on a common expression, such as "2Shae," "Page3," "2Cold," "In1," and other such names.

A name might also represent a word using an irregular spelling; for example, "Train" could be Trane or Trayne, and "Envy" could be Envie or Envee. Names can contain subtle and sometimes cryptic messages, and might incorporate the artist's initials or other letters. As well as the graffiti name, some artists include the year that they completed that tag next to the name. Bomber Tox, from London, seldom writes just Tox; it is usually Tox03, Tox04, etc. In some cases, artists dedicate or create tags or graffiti in memory of a deceased friend — for example, "DIVA Peekrevs R.I.P. JTL '99." The Borf Brigade's arrested member, John Tsombikos, claimed the "BORF" tag campaign, which gained recognition for its prevalence in DC, was in memory of his deceased friend.

Initial groundwork for the current social significance of graffiti in America began around the late 1960s. Around this time, graffiti was used as a form of expression by political activists. It was considered a cheap and easy way to make a statement, with minimal risk to the artist. Gang graffiti also rose in visibility, used by gangs to mark territory. Some gangs that made use of graffiti during this era included the Savage Skulls, La Familia, and Savage Nomads.

Towards the end of the 1960s the modern culture began to form in Philadelphia, Pennsylvania. The two graffiti artists considered to be responsible for the first true bombing are "Cool Earl" and "Cornbread." They gained much attention from the Philadelphia press and the community itself by leaving their tags written everywhere. Around 1970-71, the centre of graffiti innovation moved from Philadelphia to New York City. Once the initial foundation was laid (around 1966–1971), graffiti "pioneers" began inventing newer and more creative ways to write.

Decorative and high art

Graffiti art is now on exhibition at the Brooklyn Museum as a "contemporary art" form that began in New York's outer boroughs and reached great heights in the early '80s with the work of Crash, Lee, Daze, Keith Haring and Jean-Michel Basquiat.

It displays 22 works by New York graffiti artists, including Crash, Daze and Lady Pink. In an article in Time Out Magazine, Curator Charlotta Kotik says that she hopes that the current exhibition will cause viewers to rethink their assumptions about graffiti. Terrance Lindall, noted surrealist artist whose works for Heavy Metal Magazine and Creepy and Eerie have inspired many of these artists, goes further:

"Graffiti is revolutionary like the surrealist art I represented in my show Brave Destiny," he says, "and any revolution might be considered a crime. People who are oppressed or suppressed need an outlet, so they write on walls—it’s free... However, people also have a right to protect their property. It is a human dilemma."

In Australia, art historians have judged some local graffiti of sufficient creative merit to rank them firmly within visual art. Oxford University Press's art history text Australian Painting 1788-2000 concludes with a long discussion of graffiti's key place within contemporary visual culture, including the work of several Australian practitioners.