Merriam-Webster Collegiate Dictionary - sternum

 noun  (plural ~s or sterna)  Etymology: New Latin, from Greek sternon chest, breastbone; akin to Old High German stirna forehead, Latin sternere to spread out — more at strew  Date: 1667 a compound ventral bone or cartilage of most vertebrates other than fishes that connects the ribs or the shoulder girdle or both and in humans consists of the manubrium, gladiolus, and xiphoid process — called also breastbone