Epigenetics is the study of heritable changes in gene expression that occurs without a change in DNA sequence. The development of epigenetics makes up for the insufficiency of classic genetics and promotes the development of genetics. The interrelationship between epigenetics and genetics is like a yin-yang, which are different from each other, and cooperatively take part in regulation of critical biological processes of development and evolution, etc. They constitute the two inseparable parts of genetics. The definition, research connotation and Chinese translation of epigenetics are also discussed.