Epigenetics: the history of definitions of the word

The figure shows five definitions of the word epigenetics, starting with Waddington's epigenetic landscape, moving through Nanney's use of the word to refer to cytoplasmic inheritance, the shifting use of the word by Robin Holliday, the attempt to impose constraints by Arthur Riggs, and the back-translation epi- (above, upon) -genetics (DNA sequence) that emerged to replace the original concepts.