A cannon (plural: cannon or cannons) is any piece of artillery that uses gunpowder or other usually explosive-based propellants to launch a projectile. Cannon vary in calibre, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees, depending on their intended use on the battlefield. The word cannon is derived from several languages, in which the original definition can usually be translated as tube, cane, or reed. In the modern era, the term cannon has fallen into decline, replaced by "guns" or "artillery" if not a more specific term such as "mortar" or "howitzer", except for in the field of aerial warfare, where it is often used as shorthand for autocannon.
First invented in China, cannon were among the earliest forms of gunpowder artillery, and over time replaced siege engines—among other forms of ageing weaponry—on the battlefield. In the Middle East, the first use of the hand cannon is argued to be during the 1260 Battle of Ain Jalut between the Mamluks and Mongols. The first cannon in Europe were in use in Iberia by the mid-13th century. It was during this period, the Middle Ages, that cannon became standardized, and more effective in both the anti-infantry and siege roles. After the Middle Ages most large cannon were abandoned in favour of greater numbers of lighter, more maneuverable pieces. In addition, new technologies and tactics were developed, making most defences obsolete; this led to the construction of star forts, specifically designed to withstand artillery bombardment though these too (along with the Martello Tower) would find themselves rendered obsolete when explosive and armour piercing rounds made even these types of fortifications vulnerable.
Cannon also transformed naval warfare in the early modern period, as European navies took advantage of their firepower. As rifling became commonplace, the accuracy and destructive power of cannon was significantly increased, and they became deadlier than ever, both to infantry who belatedly had to adopt different tactics, and to ships, which had to be armoured. In World War I, the majority of combat fatalities were caused by artillery; they were also used widely in World War II. Most modern cannon are similar to those used in the Second World War, although the importance of the larger calibre weapons has declined with the development of missiles.
Cannon was widely known as the earliest form of a gun and artillery, before early firearms were invented.