A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. Nerve gas, tear gas and pepper spray are three modern examples of chemical weapons.
A chemical weapon agent (CWA) is a chemical substance whose toxic properties are used to kill, injure or incapacitate human beings. About 70 different chemicals have been used or stockpiled as chemical weapon agents during the 20th century. These agents may be in liquid, gas or solid form.