Alternative spellings

• armour (UK)

Noun

Singular armor

Plural countable and uncountable; plural armors

armor (countable and uncountable; plural armors)

1. (US, uncountable) A form of body protection that consists of a hard material that is worn around the vital areas of the body.
2. (US, uncountable) A natural form of this kind of protection on an animal's body.
3. (US, countable) A tank, or other heavy mobile assault vehicle.
4. (US, uncountable) A military formation consisting primarily of tanks or other armoured fighting vehicles.

Armour or armor (see spelling differences) is protective covering used to prevent damage from being inflicted to an individual or a vehicle through use of direct contact weapons or projectiles, usually during combat. Armour has been used to protect soldiers, war animals such as war horses (the application for the latter called barding), and war machines such as warships and armoured fighting vehicles.

Armour has been used throughout recorded history, and manufactured from a variety of materials; starting with rudimentary leather protection, personal armour evolved to mail and full plated suit of armour. For much of military history the manufacture of metal armour in Europe has dominated the technology and employment of armour. Armour production was a cause of the development of many important technologies of the Ancient World, including wood lamination, mining, metal refining, vehicle manufacture (chariot), leather processing, and later decorative metal working. Its production has been influential in the evolving industrial revolution, and influenced commercial development of metallurgy and engineering.

Armour was the single most influential factor in the development of firearms that revolutionised warfare. First modern production technology for armour plating was used by the navies in construction of the Ironclad warships, and reaching its pinnacle of development with the battleship. It was the naval engineers that also constructed the first World War I "tanks" giving rise to armoured fighting vehicles protected by vehicle armour. Air forces also sometimes employ armour. Aerial armour has been used, notably, in protecting the pilots during the Second World War, and in designing heavily armoured aircraft that would be expected to suffer more than usual damage from ground fire.

In modern ground forces' usage, the meaning of armour has expanded to include the role of troops in combat. After the evolution of armoured warfare, heavily armoured military forces are organised using armoured infantry, mounted in armoured fighting vehicles and replacing light infantry in many situations. In modern armoured warfare, armoured units equipped with tanks and infantry fighting vehicles serve the historic role of both the battle cavalry, light cavalry and dragoons, and belong to the armoured branch in a national army's organization (sometimes, the armoured corps).