Final answer:
A bursa is a sac of fluid that reduces friction between a soft tissue and a bone. It prevents rubbing of skin, muscle, or tendon against an underlying bone, reducing friction and allowing smooth movement. Bursae are located near body joints to separate and protect adjacent structures.
Step-by-step explanation:
A sac of fluid that reduces friction between a soft tissue and a bone is called a bursa. Bursae are fluid-filled sacs that prevent friction between skin, muscle, or tendon and an underlying bone. They are located in regions where these structures can rub against each other, usually near a body joint. Bursae reduce friction by separating the adjacent structures, preventing them from rubbing directly against each other.