ˌe-pə-jə-ˈne-tiks
Noun
1. Branch of biology that deals with the study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence (dictionary.com)
2. The study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence.
3. (Genetics)
The study of the processes involved in the genetic development of an organism, especially the activation and deactivation of genes. (wiktionary.com)
4. (Genetics)
The study of heritable changes caused by the activation and deactivation of genes without any change in DNA sequence. (wiktionary.com)
Word origin: From Greek epi-, επί-, over, above, outer + –genetics. (Wikipedia.org)