Notum

Part of speech: noun

Definitions

1. A part or structure in the back or upper surface of certain invertebrates, often involved in locomotion or attachment
2. Referring to a specific anatomical feature related to the dorsal aspect in various organisms, particularly among arthropods
3. Denoting the elevated or upper surface of an animal's body segment, particularly in classification and biological studies

Etymology: Before it named a plate on an insect's back, "notum" was simply the Ancient Greek word "nôton," meaning "back," as in the back of the body or the spine. The Greek noun carried that plain sense of the dorsal side of an animal, and the anatomical term borrows it directly. In zoology, the notum is the dorsal sclerite, or hardened plate, of a body segment. Arthropods such as insects, spiders and crustaceans are built from segments encased in tough armour, and each segment's back is covered by its own notum, which sits above the pleuron on the side and the sternum below. The word thus preserves the ancient idea of "back" but applies it to a single, precisely bounded piece of skeleton, one for each segment of the body.