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1660s, from Greek sternon "chest, breast, breastbone" (in Homer, only of males), from PIE *stre-to- "to stretch, extend," from a root meaning "flat surface," related to stornynai "to spread out" (see structure (n.)), on the notion of the chest as broad and flat, as opposed to the neck.
sternum ster·num (stûr'nəm)
n. pl. ster·nums or ster·na (-nə)
A long flat bone, articulating with the cartilages of the first seven ribs and with the clavicle, forming the middle part of the anterior wall of the thorax, and consisting of the corpus, manubrium, and xiphoid process. Also called breastbone.
A long, flat bone located in the center of the chest, serving as a support for the collarbone and ribs. Also called breastbone. See more at skeleton.
in the anatomy of tetrapods (four-limbed vertebrates), elongated bone in the centre of the chest that articulates with and provides support for the clavicles (collarbones) of the shoulder girdle and for the ribs. Its origin in evolution is unclear. A sternum appears in certain salamanders; it is present in most other tetrapods but lacking in legless lizards, snakes, and turtles (in which the shell provides needed support). In birds an enlarged keel develops, to which flight muscles are attached; the sternum of the bat is also keeled as an adaptation for flight