What does episternum mean?
The episternum is a technical anatomical term for a skeletal element positioned in front of, or upon, the sternum — the breastbone. In vertebrate anatomy it most often denotes the foremost portion of the sternal complex, equivalent to the manubrium in mammals, where it articulates with the clavicles and first ribs to help anchor the pectoral girdle. In entomology the same word has an entirely separate application: it names one of the lateral hardened plates, or sclerites, that make up an insect's prothorax, paired against a neighbouring plate called the epimeron. The term derives from Greek elements meaning 'upon' and 'breastbone', a construction typical of descriptive anatomy. Because its exact referent differs across animals, the word appears almost exclusively in specialist literature on comparative anatomy, palaeontology, and insect morphology rather than general usage, and careful writers specify which sense they intend.
An element at the front of the sternum in vertebrates, corresponding to the manubrium in mammals.
"The clavicles meet the episternum at the top of the chest wall."
Primarily used in comparative anatomy and palaeontology; in human anatomy the equivalent structure is usually called simply the manubrium.
In insects, one of the lateral sclerites of the prothorax.
"The shape of the episternum is a useful character in classifying ground beetles."
The plural follows the Latin neuter second declension pattern, as with 'sternum' → 'sterna'. It appears mainly in anatomical and entomological literature.
"Both episterna were well preserved in the fossil specimen."
The episternum is a bone whose name literally means 'upon the breastbone' — anatomy's way of stacking labels on labels.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of episternum
The word 'episternum' comes from New Latin, formed from the Greek prefix 'epi-' meaning 'upon' or 'in front of', combined with 'sternon', meaning 'chest' or 'breastbone'. It entered scientific Latin during the development of modern comparative anatomy, as early naturalists needed precise labels for individual skeletal elements. Its cognates include other 'epi-' compounds such as 'epidermis' and, through the shared root 'sternon', the word 'sternum' itself.
Related word forms
How episternum is actually used
A technical term confined to comparative anatomy, palaeontology, and entomology; it is not used in everyday speech, and its precise referent varies between taxonomic groups, so writers should specify whether the vertebrate or insect sense is meant.
Easily confused with episternum
The sternum is the main breastbone itself, while the episternum is a distinct element situated at the front of (or above) the sternum.