Plasma is a state of matter that is often thought of as a subset of gases, but the two states behave very differently. Like gases, plasma's have no fixed shape or volume, and are less dense than solids or liquids.May 5, 2016
In other words, plasma was first identified in a Crookes tube, and so described by Sir William Crookes in 1879 (he called it "radiant matter"). The nature of this "cathode ray" matter was subsequently identified by British physicist Sir J.J. Thomson in 1897. The term "plasma" was coined by Irving Langmuir in 1928.