| All elementary particles have a baryon number. Baryons have a +1 value and antibaryons -1. Almost all other particles have a baryon number of zero except for quarks and antiquarks which have baryon numbers of 1/3 and -1/3, respectively. The baryon number for quarks is derived from the fact that all baryons or antibaryons are composed of exactly three quarks or antiquarks.
The baryon number is always conserved in particle interaction. This is a key concept in quantum physics because it governs the restrictions as to when and how many quarks get generated with each particle interaction. | 
