A tergum (plural terga, associated adjective tergal) is the dorsal portion of an arthropod segment other than the head. The anterior edge is called the base and posterior edge is called the apex or margin. A given tergum may be divided into several plates, called tergites. (Lateral extension of the dorsal aspect of a tergite are called paranota.) So, for example, in a thoracic segment, the tergum may be divided into an anterior notum and a posterior scutellum.

In crustaceans, it is known as a pleuron when it overhangs the insertion of the limb on each side as a free plate.

The ventral portion of a segment is called the sternum.