A weapon of mass destruction (WMD) is defined as a weapon that can kill and bring significant harm to a large number of humans (or other lifeforms) and/cause great damage to man-made structures, natural structures, or the biosphere in general. The scope and application of the term has evolved and been disputed, often signifying more politically than technically. Weapons of mass destruction include chemical, biological, radiological, nuclear, and nanoweaponry.