Plasma is a state of matter that is not commonly found on Earth under normal conditions, but is abundant in the universe. Plasma is sometimes referred to as the fourth state of matter, in addition to solid, liquid, and gas.
In a plasma, a gas has been heated to such a high temperature that some or all of its atoms have been ionized, meaning they have lost one or more electrons and become positively charged ions, and the electrons are free to move independently. As a result, plasmas exhibit unique properties, such as electrical conductivity and the ability to be affected by magnetic fields.
Plasmas are found in phenomena such as lightning, flames, and stars, as well as in many human made technologies, including plasma cutting and welding, plasma televisions, and fusion reactors. Plasmas are also important in various areas of research, such as astrophysics and nuclear physics.