The sternum (pl. "sterna") or sternite is the ventral portion of a segment of an arthropod thorax or abdomen.

In insects, the sterna are usually single, large sclerites, and external. However, they can sometimes be divided in two, and may also be modified on the terminal abdominal segments so as to form part of the functional genitalia, in which case they are frequently reduced in size and development, and may become internalized and/or membranous.

The term is also used in other arhtropod groups such as crustaceans, arachnids and myriapods.

Animal anatomy | Entomology