If matter composed of quarks of positive charge, and anti-quarks have negative charge, why do we call electrons particles of matter rather than anti-matter? Is it possible that the matter-antimatter symmetry problem exists because we are actually calling something that is a particle of anti-matter, a particle of matter? Also, am I correct to assume that annihilation between particles of matter and anti-matter may not occur if they are different types of particles of each. For instance, an electron and positron will annihilate but an electron will not annihilate with another types of anti-matter. I am probably confused, but I hope someone can critique my thought process.