An occurrence in evolution that involves changes in the pace and timing of development: Heterochrony can produce changes in size and shape of an organism and might be the connection between genetics at one furthermost point and a natural selection at the other furthermost point of time.

Heterochronism refers to the departure from the usual sequence in the development of organs or parts in an organism.

In biology. in evolution, a variation from the normall sequence in the development of organs or parts; heterochrony: In Mr. Plant's biology class, the students learned about heterochronism as being the changes in stages at which processes of development are relative to members of the same species.