Nonetheless, the quanta of the Majorana equation given here are two particle species, a neutral particle and its neutral antiparticle.

Matter is constructed from very different particle species and the proportions of these vary from material to material.

It is also possible to write down relativistic Boltzmann equations for systems in which a number of particle species can collide and produce different species.

In multifluid theory, the different particle species are treated as different fluids with different pressures, densities and flow velocities.

The frozen-in conditions must be evaluated for each particle species separately.

Some believed that there is only one consistent theory which requires infinitely many particle species and whose form can be found by consistency alone.

Factors that determine the behavior include the particle species involved, the electromagnetic, gravitational, and nuclear fields controlling the system.

The factor g is determined by the particle species:

Where t is time in seconds, T is temperature in MeV and g is the effective number of particle species.

When the Standard Model is operated, it is often made a version with supersymmetry, doubling the number of particle species so far identified by particle physicists.