Final answer:
The term cost/o refers to ribs, which are critical components of the thoracic cage and are classified based on how they attach to the sternum with their costal cartilage.
Step-by-step explanation:
The term cost/o refers to ribs. Ribs are essential components of the thoracic cage, which protects vital organs such as the heart and lungs. Ribs are numbered from 1 to 12, and the various types of ribs are classified based on their attachment to the sternum. The true ribs (1-7) attach directly to the sternum via their costal cartilage. The false ribs (8-12) have costal cartilages that either attach indirectly to the sternum via the cartilage of the rib above or do not attach at all if they are floating ribs (11-12).