I assume you mean antimatter. It turns out that different elementary particles have so-called antiparticles, which have opposite values of some key properties, such as electric charge. For example, the proton has a positive electric charge; the anti-proton has a negative electric charge. The electron has a negative charge, the anti-electron (a.k.a. "positron") has a positive charge. An anti-neutron, just like a neutron, is electrically neutral, but has a difference in some other properties. When a particle meets its anti-particle, both get destroyed (and turn into radiation). Why there is apparently more matter than antimatter in the Universe is one of the great unsolved problems in physics and cosmology.
The cast of The Synth - 2010 includes: Anti Materia
Timothy Field Allen has written: 'The encyclopedia of pure materia medica' -- subject(s): Homeopathy, Materia medica, Materia medica and therapeutics, Materia medicas, Pharmacology 'Handbook of materia medica and homoeopathic therapeutics' -- subject(s): Homeopathy, Materia medicas, Materia medica and therapeutics, Materia Medica
Memento Materia was created in 1992.
Materia Magica happened in 1996.
Materia Magica was created in 1996.
Materia - album - was created in 2006.
J. Forbes Royle has written: 'Royle's manual of materia medica and therapeutics' -- subject(s): Therapeutics, Materia Medica, Materia medica 'Materia medica and therapeutics ..' -- subject(s): Therapeutics, Materia medica
Given the in game explanation of how materia is created, one would assume that all materia are natural. The black and white materia are debatable, as some fans believe that the white materia was created by the Cetra and the origin of the black materia was never specifically stated. There is also a process in Crisis Core in which materia are fused with each other, which could be considered unnatural considering that the fusion is forced.
Eclectic Materia Medica was created in 1922.
Prima Materia - album - was created in 2003.
Materia medica
You have to level up a 2 cut materia