Lethality (also called deadliness or perniciousness) is how capable something is of causing death. Most often it is used when referring to chemical weapons, biological weapons, or their toxic chemical components. The use of this term denotes the ability of these weapons to kill, but also the possibility that they may not kill. Reasons for the lethality of a weapon to be inconsistent, or expressed by percentage, can be as varied as minimized exposure to the weapon, previous exposure to the weapon minimizing susceptibility, degradation of the weapon over time and/or distance, and incorrect deployment of a multi-component weapon.