Anti-Matter

Matter composed of particles that are the counterparts of the particles composing positive matter (the matter of which this universe is composed), but have opposite charges; e.g., anti-protons instead of protons, and positrons instead of electrons. Should positive matter come in contact with an equal amount of antimatter, both will be annihilated and converted to energy. Anti-Matter makes up most of the Negative Zone.
(See Also: Wikipedia article)