Epigenetics-literally means above genetics. It is a mechanism resulting in heritable silencing of gene expression without changing the DNA (Egger, Liang, Aparicia & Jones, 2004).
Conrad Waddington first coined the term epigenetics and defined it as "All those events which lead to the unfolding of the genetic program for development.” (Holliday, 2006). It takes into account the effect environment has on phenotype.
A simple and easy way to explain epigenetics is the regulation of switches to turn on and off the expression of a gene. Environmental factors can turn on or off these switches. The underlying DNA is not changed, but the expression is changed. This can be inherited. So environmental factors, or aquired traits, can be inherited.
For example, research has shown that exposure to environmental chemicals such as dioxins, pesticides, plastics and hydrocarbons increased ovarian disease through multiple generations. Exposure to these chemicals in great grandmothers could increase the risk for great grand daughters to develop ovarian diseases (Nilsson et al., 2012).
Egger, G., Liang, G., Aparicio, A., & Jones, P. A. (2004). Epigenetics in human disease and prospects for epigenetic therapy. Nature, 429(6990), 457-463.
Holliday, R. (2006). Epigenetics: a historical overview. Epigenetics, 1(2), 76-80.
Nilsson, E., Larsen, G., Manikkam, M., Guerrero-Bosagna, C., . Savenkova, M., Skinner, M. (2012). Environmentally Induced Epigenetic Transgenerational Inheritance of Ovarian Disease. PLoS ONE, 7 (5): e36129 DOI: 10.1371/journal.pone.0036129