A more thorough explanation:

A weapon is an object or device that is used or designed to be used to harm or kill someone. It can be a physical object like a gun or a knife, or a substance like poison or a chemical agent.

• Concealed weapon: A weapon that is carried by a person but is not visible to others.
• Dangerous weapon: An object or device that is capable of causing serious bodily injury due to the way it is used.
• Deadly weapon: Any firearm or other device, instrument, material, or substance that is likely to cause death or serious physical injury.
• Deadly weapon per se: A weapon that is deadly in and of itself or would ordinarily result in death by its use.
• Lethal weapon: Another term for deadly weapon.
• Weapon of mass destruction: A weapon that is intended to kill human beings on a massive scale, without discriminating between combatants and noncombatants. Examples include nuclear weapons and chemical weapons.

For example, a gun is a deadly weapon because it is designed to fire bullets that can cause serious injury or death. A knife is also a deadly weapon because it can be used to stab or slash someone. Poison is a dangerous weapon because it can cause serious harm if ingested or inhaled. A nuclear bomb is a weapon of mass destruction because it is designed to kill large numbers of people indiscriminately.