Weapon
Massive numbers of new designs and concepts were fielded, and all existing technologies were improved between 1939 and 1945. The most powerful weapon invented during this period was the nuclear bomb; however, many other weapons influenced the world, such as jet aircraft and radar, but were overshadowed by the visibility of nuclear weapons and long-range rockets.

Nuclear weapons: Since the realization of mutual assured destruction (MAD), the nuclear option of all-out war is no longer considered a survivable scenario. During the Cold War in the years following World War II, both the United States and the Soviet Union engaged in a nuclear arms race. Each country and their allies continually attempted to out-develop each other in the field of nuclear armaments. Once the joint technological capabilities reached the point of being able to ensure the destruction of the Earth by 100 fold, a new tactic had to be developed. With this realization, armaments development funding shifted back to primarily sponsoring the development of conventional arms technologies for support of limited wars rather than total war.

Types: 

By user: – what person or unit uses the weapon
Personal weapons (or small arms) – designed to be used by a single person.
Light weapons – 'man-portable' weapons that may require a small team to operate.
Heavy weapons – artillery and similar weapons larger than light weapons (see SALW).
Crew served weapons – larger than personal weapons, requiring two or more people to operate correctly.
Fortification weapons – mounted in a permanent installation or used primarily within a fortification.
Mountain weapons – for use by mountain forces or those operating in difficult terrain.
Vehicle weapons – to be mounted on any type of combat vehicle.
Railway weapons – designed to be mounted on railway cars, including armored trains.
Aircraft weapons – carried on and used by some type of aircraft, helicopter, or other aerial vehicle.
Naval weapons – mounted on ships and submarines.
Space weapons – are designed to be used in or launched from space.
Autonomous weapons – are capable of accomplishing a mission with limited or no human intervention.

By function: – the construction of the weapon and the principle of operation
Antimatter weapons (theoretical) – would combine matter and antimatter to cause a powerful explosion.
Archery weapons – operate by using a tensioned string and a bent solid to launch a projectile.
Artillery – firearms capable of launching heavy projectiles over long distances.
Biological weapons – spread biological agents, causing disease or infection.
Chemical weapons – poison people and cause reactions.
Energy weapons – rely on concentrating forms of energy to attack, such as lasers or sonic attacks.
Explosive weapons – use a physical explosion to create a blast, concussion, or spread shrapnel.
Firearms – use a chemical charge to launch projectiles.
Improvised weapons – common objects reused as weapons, such as crowbars and kitchen knives.
Incendiary weapons – cause damage by fire.
Non-lethal weapons – designed to subdue without killing.
Magnetic weapons – use magnetic fields to propel projectiles or focus particle beams.
Melee weapons – operate as physical extensions of the user's body and directly impact a close target.
Blade weapons – designed to pierce or cut through skin, muscle, or bone and cause internal or external bleeding.
Blunt instruments – designed to break or fracture bones, produce concussions, create organ ruptures, or crush injuries.
Missiles – rockets that are guided to their target after launch. (Also a general term for projectile weapons.)
Loitering munitions – designed to loiter over a battlefield, striking once a target is located.
Nuclear weapons – use radioactive materials to create nuclear fission or nuclear fusion detonations
Ranged weapons – (unlike melee weapons) target a distant object or person.
Rockets – self-propelled projectiles.
Suicide weapons – exploit the willingness of their operators not surviving the attack.

By target: – the type of target the weapon is designed to attack
Anti-aircraft weapons – target missiles and aerial vehicles in flight.
Anti-fortification weapons – designed to target enemy installations.
Anti-personnel weapons – designed to attack people, either individually or in numbers.
Anti-radiation weapons – target sources of electronic radiation, particularly radar emitters.
Anti-satellite weapons – target orbiting satellites.
Anti-ship weapons – target ships and vessels on water.
Anti-submarine weapons – target submarines and other underwater targets.
Anti-tank weapons – designed to defeat armored targets.
Area denial weapons – target territory, making it unsafe or unsuitable for enemy use or travel.
Hunting weapons – weapons used to hunt game animals.
Infantry support weapons – designed to attack various threats to infantry units.
Siege engines – designed to break or circumvent heavy fortifications in siege warfare.

Manufacture of weapons: The arms industry is a global industry that involves the sale and manufacture of weaponry. It consists of a commercial industry involved in the research and development, engineering, production, and servicing of military material, equipment, and facilities. Many industrialized countries have a domestic arms industry to supply their own military forces, and some also have a substantial trade in weapons for use by their citizens for self-defense, hunting, or sporting purposes.
Contracts to supply a given country's military are awarded by governments, making arms contracts of substantial political importance. The link between politics and the arms trade can result in the development of a "military–industrial complex", where the armed forces, commerce, and politics become closely linked.
According to research institute SIPRI, the volume of international transfers of major weapons in 2010–2014 was 16 percent higher than in 2005–2009, and the arms sales of the world's 100 largest private arms-producing and military services companies totaled $420 billion in 2018.

Legislation: The production, possession, trade, and use of many weapons are controlled. This may be at a local or central government level or by international treaty. Examples of such controls include:

Gun laws: All countries have laws and policies regulating aspects such as the manufacture, sale, transfer, possession, modification, and use of small arms by civilians.
Countries that regulate access to firearms will typically restrict access to certain categories of firearms and then restrict the categories of persons who may be granted a license for access to such firearms. There may be separate licenses for hunting, sport shooting (a.k.a. target shooting), self-defense, collecting, and concealed carry, with different sets of requirements, permissions, and responsibilities.

Arms control laws: International treaties and agreements place restrictions on the development, production, stockpiling, proliferation, and usage of weapons, from small arms and heavy weapons to weapons of mass destruction. Arms control is typically exercised through the use of diplomacy, which seeks to impose such limitations upon consenting participants, although it may also comprise efforts by a nation or group of nations to enforce limitations upon a non-consenting country.

Arms trafficking laws: Arms trafficking is the trafficking of contraband weapons and ammunition. What constitutes legal trade in firearms varies widely, depending on local and national laws. In 2001, the United Nations had made a protocol against the manufacturing and trafficking of illicit arms. This protocol made governments dispose illegal arms, and to licence new firearms being produced, to ensure them being legitimate. It was signed by 122 parties.

Lifecycle problems: There are a number of issues around the potential ongoing risks from deployed weapons, the safe storage of weapons, and their eventual disposal when they are no longer effective or safe.

Ocean dumping of unused weapons such as bombs, ordnance, landmines, and chemical weapons has been common practice by many nations and has created hazards.
Unexploded ordnance (UXO) are bombs, land mines, naval mines, and similar devices that did not explode when they were employed and still pose a risk for many years or decades.
Demining or mine clearance from areas of past conflict is a difficult process, but every year, landmines kill 15,000 to 20,000 people and severely maim countless more.
Nuclear terrorism was a serious concern after the fall of the Soviet Union, with the prospect of "loose nukes" being available. While this risk may have receded, similar situations may arise in the future.

In science fiction: Strange and exotic weapons are a recurring feature or theme in science fiction. In some cases, weapons first introduced in science fiction have now become a reality. Other science fiction weapons, such as force fields and stasis fields, remain purely fictional and are often beyond the realms of known physical possibility.
At its most prosaic, science fiction features an endless variety of sidearms, mostly variations on real weapons such as guns and swords. Among the best-known of these are the phaser used in the Star Trek television series, films, and novels, and the lightsaber and blaster featured in the Star Wars movies, comics, novels, and TV series.
In addition to adding action and entertainment value, weaponry in science fiction sometimes becomes a theme when it touches on deeper concerns, often motivated by contemporary issues. One example is science fiction that deals with weapons of mass destruction like doomsday devices.

See also: 

References: Weapon Specialist – Weapon Expert. Bevic Huynh, New York, 2012.. Retrieved July 26, 2012.

External links:  The dictionary definition of weapon at Wiktionary
 Quotations related to Weapon at Wikiquote
 Media related to Weapons at Wikimedia Commons