A bomb is any of a range of explosive weapons that only rely on the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy (an explosive device). Detonations inflict damage principally through ground- and atmosphere-transmitted mechanical stress, the impact and penetration of pressure-driven projectiles, pressure damage, and explosion-generated effects. A nuclear weapon employs chemical-based explosives to initiate a much larger nuclear-based explosion. Bombs have been in use since the 11th century in Song Dynasty China.
The term bomb is not usually applied to explosive devices used for civilian purposes such as construction or mining, although the people using the devices may sometimes refer to them as "bomb". The military use of the term "bomb", or more specifically aerial bomb action, typically refers to airdropped, unpowered explosive weapons most commonly used by air forces and naval aviation. Other military explosive weapons not classified as "bombs" includegrenades, shells, depth charges (used in water), warheads when in missiles, or land mines. In unconventional warfare, "bomb" can refer to a range of offensive weaponry. For instance, in recent conflicts, "bombs" known as improvised explosive devices (IEDS) have been employed by insurgent fighters to great effectiveness.