Graffiti (strictly, as singular, "graffito," from the Italian — "graffiti" being the plural) are images or letters applied without permission to publicly viewable surfaces such as walls or bridges. Graffiti has existed at least since the days of ancient civilizations such as Ancient Greece and the Roman Empire. Graffiti has changed over time into what are known as "modern graffiti": the public defacing of a surface using spray paint, markers, or other materials. When graffiti painting is done without the property owner's consent, it can be considered vandalism, which is punishable by law in most countries.
Graffiti can be used to communicate social and political messages, and as a form of advertising. It is also considered a modern art form, and can be seen in galleries around the world.