When the structure of an animal's body shows repeating segments it is known as a metamere (metamerism).
Metamerism (also called segmentation) is a condition in which the structure of an animal's body shows linear series of repeating parts. Each of the body segments is known as a metamere or somites, and they are formed individually in sequence in the embryo. All organisms that belongs to the three large animal phyla which are; Chordata, Arthropoda, and Annelida are metameric.