Epigenetics
The term "epigenetics" has been used to describe processes which are not heritable. An example is histone modification. So some definitions do not require heritability. Adrian Bird defined epigenetics as "the structural adaptation of chromosomal regions so as to register, signal or perpetuate altered activity states". This definition includes DNA repair or cell division phases, and stable changes across cell generations. It excludes others such as prions unless they affect chromosome function.