Costae

Part of speech: noun

Pronunciation: /ˈkɑˌsti/

Definitions

1. A pair of structures that provide support to certain anatomical features, particularly in the ribcage or related areas
2. Rows of bony elements that contribute to the framework of specific organisms, being essential for protection and movement
3. Arrangements of support structures found in biological forms, commonly associated with the skeletal system and respiratory function

Etymology: "Costae" is simply the Latin plural of "costa," meaning "a rib," so the English word keeps a Latin plural that was never anglicised. The singular "costa" was taken directly from Latin, and it is a doublet of "coast": the two words descend from the same Latin source but reached English by different routes. The rib sense came in through the scientific vocabulary of anatomy, while "coast" arrived through French and kept the sense of a shoreline, which the Latin word "costa" also carried, in the sense of a side or edge. The sense of "rib" and "side" connects naturally. A ship's coast and a body's ribs both describe a long, curved boundary that flanks something larger, and the Latin word ran through both meanings. In anatomy, the plural form is the one used when referring to several ribs or to the ribbed structures of a shell, leaf or other organism.