This post is also available in: Japanese
Plasma is the volume exceeding the average distance covered by the interaction between the two charged particles, in a system containing two or more charged particle groups of different signs of charge, where at least one of which is undergoing irregular thermal motion.
The total charge of electrons in the plasma and the total charge of positive ions are electrically neutral, as they have opposite signs and equal magnitude. Plasma is also referred to as the fourth state of matter, as it has unique properties that are different from any other states of matter – solid, liquid, or gas.